This patch series adds support for PCI pass-thru devices to Hyper-V
Confidential VMs (also called "Isolation VMs"). But in preparation, it
first changes how private (encrypted) vs. shared (decrypted) memory is
handled in Hyper-V SEV-SNP guest VMs. The new approach builds on the
confidential computing (coco) mechanisms introduced in the 5.19 kernel
for TDX support and significantly reduces the amount of Hyper-V specific
code. Furthermore, with this new approach a proposed RFC patch set for
generic DMA layer functionality[1] is no longer necessary.
Background
==========
Hyper-V guests on AMD SEV-SNP hardware have the option of using the
"virtual Top Of Memory" (vTOM) feature specified by the SEV-SNP
architecture. With vTOM, shared vs. private memory accesses are
controlled by splitting the guest physical address space into two
halves. vTOM is the dividing line where the uppermost bit of the
physical address space is set; e.g., with 47 bits of guest physical
address space, vTOM is 0x40000000000 (bit 46 is set). Guest phyiscal
memory is accessible at two parallel physical addresses -- one below
vTOM and one above vTOM. Accesses below vTOM are private (encrypted)
while accesses above vTOM are shared (decrypted). In this sense, vTOM
is like the GPA.SHARED bit in Intel TDX.
In Hyper-V's use of vTOM, the normal guest OS runs at VMPL2, while
a Hyper-V provided "paravisor" runs at VMPL0 in the guest VM. (VMPL is
Virtual Machine Privilege Level. See AMD's SEV-SNP spec for more
details.) The paravisor provides emulation for various system devices
like the I/O APIC as part of the guest VM. Accesses to such devices
made by the normal guest OS trap to the paravisor and are emulated in
the guest VM context instead of in the Hyper-V host. This emulation is
invisible to the normal guest OS, but with the quirk that memory mapped
I/O accesses to these devices must be treated as private, not shared as
would be the case for other device accesses.
Support for Hyper-V guests using vTOM was added to the Linux kernel
in two patch sets[2][3]. This support treats the vTOM bit as part of
the physical address. For accessing shared (decrypted) memory, the core
approach is to create a second kernel virtual mapping that maps to
parallel physical addresses above vTOM, while leaving the original
mapping unchanged. Most of the code for creating that second virtual
mapping is confined to Hyper-V specific areas, but there are are also
changes to generic swiotlb code.
Changes in this patch set
=========================
In preparation for supporting PCI pass-thru devices, this patch set
changes the core approach for handling vTOM. In the new approach,
the vTOM bit is treated as a protection flag, and not as part of
the physical address. This new approach is like the approach for
the GPA.SHARED bit in Intel TDX. Furthermore, there's no need to
create a second kernel virtual mapping. When memory is changed
between private and shared using set_memory_decrypted() and
set_memory_encrypted(), the PTEs for the existing kernel mapping
are changed to add or remove the vTOM bit just as with TDX. The
hypercalls to change the memory status on the host side are made
using the existing callback mechanism. Everything just works, with
a minor tweak to map the I/O APIC to use private accesses as mentioned
above.
With the new handling of vTOM in place, existing Hyper-V code that
creates the second kernel virtual mapping still works, but it is now
redundant as the original kernel virtual mapping (as updated) maps
to the same physical address. To simplify things going forward, this
patch set removes the code that creates the second kernel virtual
mapping. And since a second kernel virtual mapping is no longer
needed, the changes to the DMA layer proposed as an RFC[1] are no
longer needed.
Finally, to support PCI pass-thru in a Confidential VM, Hyper-V
requires that all accesses to PCI config space be emulated using
a hypercall. This patch set adds functions to invoke those
hypercalls and uses them in the config space access functions
in the Hyper-V PCI driver. Lastly, the Hyper-V PCI driver is
marked as allowed to be used in a Confidential VM. The Hyper-V
PCI driver has been hardened against a malicious Hyper-V in a
previous patch set.[4]
Patch Organization
==================
Patch 1 fixes a bug in __ioremap_caller() that affects the
existing Hyper-V code after the change to treat the vTOM bit as
a protection flag. Fixing the bug allows the old code to continue
to run until later patches in the series remove or update it.
This sequencing avoids the need to enable the new approach and
remove the old code in a single large patch.
Patch 2 handles the I/O APIC quirk by defining a new CC_ATTR enum
member that is set only when running on Hyper-V.
Patch 3 does some simple reordering of code to facilitate Patch 5.
Patch 4 tweaks calls to vmap_pfn() in the old Hyper-V code that
are deleted in later patches in the series. Like Patch 1, this
patch helps avoid the need to enable the new approach and remove
the old code in a single large patch.
Patch 5 enables the new approach to handling vTOM for Hyper-V
guest VMs.
Patches 6 thru 9 remove existing code for creating a second
kernel virtual mapping.
Patch 10 updates existing code so that it no longer assumes that
the vTOM bit is part of the physical address.
Patch 11 adds the new hypercalls for accessing MMIO Config Space.
Patch 12 updates the PCI Hyper-V driver to use the new hypercalls
and enables the PCI Hyper-V driver to be used in a Confidential VM.
[1] https://lore.kernel.org/lkml/[email protected]/
[2] https://lore.kernel.org/all/[email protected]/
[3] https://lore.kernel.org/all/[email protected]/
[4] https://lore.kernel.org/all/[email protected]/
Michael Kelley (12):
x86/ioremap: Fix page aligned size calculation in __ioremap_caller()
x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute
x86/hyperv: Reorder code in prep for subsequent patch
Drivers: hv: Explicitly request decrypted in vmap_pfn() calls
x86/hyperv: Change vTOM handling to use standard coco mechanisms
swiotlb: Remove bounce buffer remapping for Hyper-V
Drivers: hv: vmbus: Remove second mapping of VMBus monitor pages
Drivers: hv: vmbus: Remove second way of mapping ring buffers
hv_netvsc: Remove second mapping of send and recv buffers
Drivers: hv: Don't remap addresses that are above shared_gpa_boundary
PCI: hv: Add hypercalls to read/write MMIO space
PCI: hv: Enable PCI pass-thru devices in Confidential VMs
arch/x86/coco/core.c | 10 +-
arch/x86/hyperv/hv_init.c | 7 +-
arch/x86/hyperv/ivm.c | 121 ++++++++++----------
arch/x86/include/asm/hyperv-tlfs.h | 3 +
arch/x86/include/asm/mshyperv.h | 8 +-
arch/x86/kernel/apic/io_apic.c | 3 +-
arch/x86/kernel/cpu/mshyperv.c | 22 ++--
arch/x86/mm/ioremap.c | 2 +-
arch/x86/mm/pat/set_memory.c | 6 +-
drivers/hv/Kconfig | 1 -
drivers/hv/channel_mgmt.c | 2 +-
drivers/hv/connection.c | 113 +++++--------------
drivers/hv/hv.c | 23 ++--
drivers/hv/hv_common.c | 11 --
drivers/hv/hyperv_vmbus.h | 2 -
drivers/hv/ring_buffer.c | 62 ++++-------
drivers/net/hyperv/hyperv_net.h | 2 -
drivers/net/hyperv/netvsc.c | 48 +-------
drivers/pci/controller/pci-hyperv.c | 215 +++++++++++++++++++++++++-----------
include/asm-generic/hyperv-tlfs.h | 22 ++++
include/asm-generic/mshyperv.h | 2 -
include/linux/cc_platform.h | 13 +++
include/linux/swiotlb.h | 2 -
kernel/dma/swiotlb.c | 45 +-------
24 files changed, 343 insertions(+), 402 deletions(-)
--
1.8.3.1
If applying the PHYSICAL_PAGE_MASK to the phys_addr argument causes
upper bits to be masked out, the re-calculation of size to account for
page alignment is incorrect because the same bits are not masked out
in last_addr.
Fix this by masking the page aligned last_addr as well.
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/mm/ioremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 78c5bc6..0343de4 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -218,7 +218,7 @@ static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
*/
offset = phys_addr & ~PAGE_MASK;
phys_addr &= PHYSICAL_PAGE_MASK;
- size = PAGE_ALIGN(last_addr+1) - phys_addr;
+ size = (PAGE_ALIGN(last_addr+1) & PHYSICAL_PAGE_MASK) - phys_addr;
retval = memtype_reserve(phys_addr, (u64)phys_addr + size,
pcm, &new_pcm);
--
1.8.3.1
Current code always maps the IOAPIC as shared (decrypted) in a
confidential VM. But Hyper-V guest VMs on AMD SEV-SNP with vTOM
enabled use a paravisor running in VMPL0 to emulate the IOAPIC.
In such a case, the IOAPIC must be accessed as private (encrypted).
Fix this by gating the IOAPIC decrypted mapping on a new
cc_platform_has() attribute that a subsequent patch in the series
will set only for Hyper-V guests. The new attribute is named
somewhat generically because similar paravisor emulation cases
may arise in the future.
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/kernel/apic/io_apic.c | 3 ++-
include/linux/cc_platform.h | 13 +++++++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a868b76..d2c1bf7 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2686,7 +2686,8 @@ static void io_apic_set_fixmap(enum fixed_addresses idx, phys_addr_t phys)
* Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot
* bits, just like normal ioremap():
*/
- flags = pgprot_decrypted(flags);
+ if (!cc_platform_has(CC_ATTR_HAS_PARAVISOR))
+ flags = pgprot_decrypted(flags);
__set_fixmap(idx, phys, flags);
}
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd..b6c4a79 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h
@@ -90,6 +90,19 @@ enum cc_attr {
* Examples include TDX Guest.
*/
CC_ATTR_HOTPLUG_DISABLED,
+
+ /**
+ * @CC_ATTR_HAS_PARAVISOR: Guest VM is running with a paravisor
+ *
+ * The platform/OS is running as a guest/virtual machine with
+ * a paravisor in VMPL0. Having a paravisor affects things
+ * like whether the I/O APIC is emulated and operates in the
+ * encrypted or decrypted portion of the guest physical address
+ * space.
+ *
+ * Examples include Hyper-V SEV-SNP guests using vTOM.
+ */
+ CC_ATTR_HAS_PARAVISOR,
};
#ifdef CONFIG_ARCH_HAS_CC_PLATFORM
--
1.8.3.1
With changes to how Hyper-V guest VMs flip memory between private
(encrypted) and shared (decrypted), creating a second kernel virtual
mapping for shared memory is no longer necessary. Everything needed
for the transition to shared is handled by set_memory_decrypted().
As such, remove the code to create and manage the second
mapping for the pre-allocated send and recv buffers. This mapping
is the last user of hv_map_memory()/hv_unmap_memory(), so delete
these functions as well. Finally, hv_map_memory() is the last
user of vmap_pfn() in Hyper-V guest code, so remove the Kconfig
selection of VMAP_PFN.
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/hyperv/ivm.c | 28 ------------------------
drivers/hv/Kconfig | 1 -
drivers/hv/hv_common.c | 11 ----------
drivers/net/hyperv/hyperv_net.h | 2 --
drivers/net/hyperv/netvsc.c | 48 ++---------------------------------------
include/asm-generic/mshyperv.h | 2 --
6 files changed, 2 insertions(+), 90 deletions(-)
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 29ccbe8..5e4b8b0 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -349,34 +349,6 @@ void __init hv_vtom_init(void)
#endif /* CONFIG_AMD_MEM_ENCRYPT */
-/*
- * hv_map_memory - map memory to extra space in the AMD SEV-SNP Isolation VM.
- */
-void *hv_map_memory(void *addr, unsigned long size)
-{
- unsigned long *pfns = kcalloc(size / PAGE_SIZE,
- sizeof(unsigned long), GFP_KERNEL);
- void *vaddr;
- int i;
-
- if (!pfns)
- return NULL;
-
- for (i = 0; i < size / PAGE_SIZE; i++)
- pfns[i] = vmalloc_to_pfn(addr + i * PAGE_SIZE) +
- (ms_hyperv.shared_gpa_boundary >> PAGE_SHIFT);
-
- vaddr = vmap_pfn(pfns, size / PAGE_SIZE, pgprot_decrypted(PAGE_KERNEL_NOENC));
- kfree(pfns);
-
- return vaddr;
-}
-
-void hv_unmap_memory(void *addr)
-{
- vunmap(addr);
-}
-
enum hv_isolation_type hv_get_isolation_type(void)
{
if (!(ms_hyperv.priv_high & HV_ISOLATION))
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 0747a8f..9a074cb 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -8,7 +8,6 @@ config HYPERV
|| (ARM64 && !CPU_BIG_ENDIAN))
select PARAVIRT
select X86_HV_CALLBACK_VECTOR if X86
- select VMAP_PFN
help
Select this option to run Linux as a Hyper-V client operating
system.
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index ae68298..566735f 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -308,14 +308,3 @@ u64 __weak hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_s
return HV_STATUS_INVALID_PARAMETER;
}
EXPORT_SYMBOL_GPL(hv_ghcb_hypercall);
-
-void __weak *hv_map_memory(void *addr, unsigned long size)
-{
- return NULL;
-}
-EXPORT_SYMBOL_GPL(hv_map_memory);
-
-void __weak hv_unmap_memory(void *addr)
-{
-}
-EXPORT_SYMBOL_GPL(hv_unmap_memory);
diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index dd5919e..33d51e3 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -1139,7 +1139,6 @@ struct netvsc_device {
/* Receive buffer allocated by us but manages by NetVSP */
void *recv_buf;
- void *recv_original_buf;
u32 recv_buf_size; /* allocated bytes */
struct vmbus_gpadl recv_buf_gpadl_handle;
u32 recv_section_cnt;
@@ -1148,7 +1147,6 @@ struct netvsc_device {
/* Send buffer allocated by us */
void *send_buf;
- void *send_original_buf;
u32 send_buf_size;
struct vmbus_gpadl send_buf_gpadl_handle;
u32 send_section_cnt;
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 9352dad..661bbe6 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -154,17 +154,8 @@ static void free_netvsc_device(struct rcu_head *head)
int i;
kfree(nvdev->extension);
-
- if (nvdev->recv_original_buf)
- vfree(nvdev->recv_original_buf);
- else
- vfree(nvdev->recv_buf);
-
- if (nvdev->send_original_buf)
- vfree(nvdev->send_original_buf);
- else
- vfree(nvdev->send_buf);
-
+ vfree(nvdev->recv_buf);
+ vfree(nvdev->send_buf);
bitmap_free(nvdev->send_section_map);
for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
@@ -347,7 +338,6 @@ static int netvsc_init_buf(struct hv_device *device,
struct nvsp_message *init_packet;
unsigned int buf_size;
int i, ret = 0;
- void *vaddr;
/* Get receive buffer area. */
buf_size = device_info->recv_sections * device_info->recv_section_size;
@@ -383,17 +373,6 @@ static int netvsc_init_buf(struct hv_device *device,
goto cleanup;
}
- if (hv_isolation_type_snp()) {
- vaddr = hv_map_memory(net_device->recv_buf, buf_size);
- if (!vaddr) {
- ret = -ENOMEM;
- goto cleanup;
- }
-
- net_device->recv_original_buf = net_device->recv_buf;
- net_device->recv_buf = vaddr;
- }
-
/* Notify the NetVsp of the gpadl handle */
init_packet = &net_device->channel_init_pkt;
memset(init_packet, 0, sizeof(struct nvsp_message));
@@ -497,17 +476,6 @@ static int netvsc_init_buf(struct hv_device *device,
goto cleanup;
}
- if (hv_isolation_type_snp()) {
- vaddr = hv_map_memory(net_device->send_buf, buf_size);
- if (!vaddr) {
- ret = -ENOMEM;
- goto cleanup;
- }
-
- net_device->send_original_buf = net_device->send_buf;
- net_device->send_buf = vaddr;
- }
-
/* Notify the NetVsp of the gpadl handle */
init_packet = &net_device->channel_init_pkt;
memset(init_packet, 0, sizeof(struct nvsp_message));
@@ -762,12 +730,6 @@ void netvsc_device_remove(struct hv_device *device)
netvsc_teardown_send_gpadl(device, net_device, ndev);
}
- if (net_device->recv_original_buf)
- hv_unmap_memory(net_device->recv_buf);
-
- if (net_device->send_original_buf)
- hv_unmap_memory(net_device->send_buf);
-
/* Release all resources */
free_netvsc_device_rcu(net_device);
}
@@ -1831,12 +1793,6 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
netif_napi_del(&net_device->chan_table[0].napi);
cleanup2:
- if (net_device->recv_original_buf)
- hv_unmap_memory(net_device->recv_buf);
-
- if (net_device->send_original_buf)
- hv_unmap_memory(net_device->send_buf);
-
free_netvsc_device(&net_device->rcu);
return ERR_PTR(ret);
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index bfb9eb9..6fabc4a 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -267,8 +267,6 @@ static inline int cpumask_to_vpset_noself(struct hv_vpset *vpset,
void hyperv_cleanup(void);
bool hv_query_ext_cap(u64 cap_query);
void hv_setup_dma_ops(struct device *dev, bool coherent);
-void *hv_map_memory(void *addr, unsigned long size);
-void hv_unmap_memory(void *addr);
#else /* CONFIG_HYPERV */
static inline bool hv_is_hyperv_initialized(void) { return false; }
static inline bool hv_is_hibernation_supported(void) { return false; }
--
1.8.3.1
Reorder some code as preparation for a subsequent patch. No
functional change.
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/hyperv/ivm.c | 68 +++++++++++++++++++++++++--------------------------
1 file changed, 34 insertions(+), 34 deletions(-)
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 1dbcbd9..f33c67e 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -235,40 +235,6 @@ void hv_ghcb_msr_read(u64 msr, u64 *value)
EXPORT_SYMBOL_GPL(hv_ghcb_msr_read);
#endif
-enum hv_isolation_type hv_get_isolation_type(void)
-{
- if (!(ms_hyperv.priv_high & HV_ISOLATION))
- return HV_ISOLATION_TYPE_NONE;
- return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
-}
-EXPORT_SYMBOL_GPL(hv_get_isolation_type);
-
-/*
- * hv_is_isolation_supported - Check system runs in the Hyper-V
- * isolation VM.
- */
-bool hv_is_isolation_supported(void)
-{
- if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
- return false;
-
- if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
- return false;
-
- return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
-}
-
-DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
-
-/*
- * hv_isolation_type_snp - Check system runs in the AMD SEV-SNP based
- * isolation VM.
- */
-bool hv_isolation_type_snp(void)
-{
- return static_branch_unlikely(&isolation_type_snp);
-}
-
/*
* hv_mark_gpa_visibility - Set pages visible to host via hvcall.
*
@@ -387,3 +353,37 @@ void hv_unmap_memory(void *addr)
{
vunmap(addr);
}
+
+enum hv_isolation_type hv_get_isolation_type(void)
+{
+ if (!(ms_hyperv.priv_high & HV_ISOLATION))
+ return HV_ISOLATION_TYPE_NONE;
+ return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
+}
+EXPORT_SYMBOL_GPL(hv_get_isolation_type);
+
+/*
+ * hv_is_isolation_supported - Check system runs in the Hyper-V
+ * isolation VM.
+ */
+bool hv_is_isolation_supported(void)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
+ return false;
+
+ if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
+ return false;
+
+ return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
+}
+
+DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
+
+/*
+ * hv_isolation_type_snp - Check system runs in the AMD SEV-SNP based
+ * isolation VM.
+ */
+bool hv_isolation_type_snp(void)
+{
+ return static_branch_unlikely(&isolation_type_snp);
+}
--
1.8.3.1
To support PCI pass-thru devices in Confidential VMs, Hyper-V
has added hypercalls to read and write MMIO space. Add the
appropriate definitions to hyperv-tlfs.h and implement
functions to make the hypercalls. These functions are used
in a subsequent patch.
Co-developed-by: Dexuan Cui <[email protected]>
Signed-off-by: Dexuan Cui <[email protected]>
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/include/asm/hyperv-tlfs.h | 3 ++
drivers/pci/controller/pci-hyperv.c | 62 +++++++++++++++++++++++++++++++++++++
include/asm-generic/hyperv-tlfs.h | 22 +++++++++++++
3 files changed, 87 insertions(+)
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 3089ec3..f769b9d 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -117,6 +117,9 @@
/* Recommend using enlightened VMCS */
#define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED BIT(14)
+/* Use hypercalls for MMIO config space access */
+#define HV_X64_USE_MMIO_HYPERCALLS BIT(21)
+
/*
* CPU management features identification.
* These are HYPERV_CPUID_CPU_MANAGEMENT_FEATURES.EAX bits.
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index e7c6f66..02ebf3e 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1054,6 +1054,68 @@ static int wslot_to_devfn(u32 wslot)
return PCI_DEVFN(slot_no.bits.dev, slot_no.bits.func);
}
+static void hv_pci_read_mmio(phys_addr_t gpa, int size, u32 *val)
+{
+ struct hv_mmio_read_input *in;
+ struct hv_mmio_read_output *out;
+ u64 ret;
+
+ /*
+ * Must be called with interrupts disabled so it is safe
+ * to use the per-cpu input argument page. Use it for
+ * both input and output.
+ */
+ in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+ out = *this_cpu_ptr(hyperv_pcpu_input_arg) + sizeof(*in);
+ in->gpa = gpa;
+ in->size = size;
+
+ ret = hv_do_hypercall(HVCALL_MMIO_READ, in, out);
+ if (hv_result_success(ret)) {
+ switch (size) {
+ case 1:
+ *val = *(u8 *)(out->data);
+ break;
+ case 2:
+ *val = *(u16 *)(out->data);
+ break;
+ default:
+ *val = *(u32 *)(out->data);
+ break;
+ }
+ } else
+ pr_err("MMIO read hypercall failed with status %llx\n", ret);
+}
+
+static void hv_pci_write_mmio(phys_addr_t gpa, int size, u32 val)
+{
+ struct hv_mmio_write_input *in;
+ u64 ret;
+
+ /*
+ * Must be called with interrupts disabled so it is safe
+ * to use the per-cpu input argument memory.
+ */
+ in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+ in->gpa = gpa;
+ in->size = size;
+ switch (size) {
+ case 1:
+ *(u8 *)(in->data) = val;
+ break;
+ case 2:
+ *(u16 *)(in->data) = val;
+ break;
+ default:
+ *(u32 *)(in->data) = val;
+ break;
+ }
+
+ ret = hv_do_hypercall(HVCALL_MMIO_WRITE, in, NULL);
+ if (!hv_result_success(ret))
+ pr_err("MMIO write hypercall failed with status %llx\n", ret);
+}
+
/*
* PCI Configuration Space for these root PCI buses is implemented as a pair
* of pages in memory-mapped I/O space. Writing to the first page chooses
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index fdce7a4..383b620 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -159,6 +159,8 @@ struct ms_hyperv_tsc_page {
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
#define HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY 0x00db
+#define HVCALL_MMIO_READ 0x0106
+#define HVCALL_MMIO_WRITE 0x0107
/* Extended hypercalls */
#define HV_EXT_CALL_QUERY_CAPABILITIES 0x8001
@@ -781,4 +783,24 @@ struct hv_memory_hint {
union hv_gpa_page_range ranges[];
} __packed;
+/* Data structures for HVCALL_MMIO_READ and HVCALL_MMIO_WRITE */
+#define HV_HYPERCALL_MMIO_MAX_DATA_LENGTH 64
+
+struct hv_mmio_read_input {
+ u64 gpa;
+ u32 size;
+ u32 reserved;
+} __packed;
+
+struct hv_mmio_read_output {
+ u8 data[HV_HYPERCALL_MMIO_MAX_DATA_LENGTH];
+} __packed;
+
+struct hv_mmio_write_input {
+ u64 gpa;
+ u32 size;
+ u32 reserved;
+ u8 data[HV_HYPERCALL_MMIO_MAX_DATA_LENGTH];
+} __packed;
+
#endif
--
1.8.3.1
Hyper-V guests on AMD SEV-SNP hardware have the option of using the
"virtual Top Of Memory" (vTOM) feature specified by the SEV-SNP
architecture. With vTOM, shared vs. private memory accesses are
controlled by splitting the guest physical address space into two
halves. vTOM is the dividing line where the uppermost bit of the
physical address space is set; e.g., with 47 bits of guest physical
address space, vTOM is 0x40000000000 (bit 46 is set). Guest phyiscal
memory is accessible at two parallel physical addresses -- one below
vTOM and one above vTOM. Accesses below vTOM are private (encrypted)
while accesses above vTOM are shared (decrypted). In this sense, vTOM
is like the GPA.SHARED bit in Intel TDX.
Support for Hyper-V guests using vTOM was added to the Linux kernel in
two patch sets[1][2]. This support treats the vTOM bit as part of
the physical address. For accessing shared (decrypted) memory, these
patch sets create a second kernel virtual mapping that maps to physical
addresses above vTOM.
A better approach is to treat the vTOM bit as a protection flag, not
as part of the physical address. This new approach is like the approach
for the GPA.SHARED bit in Intel TDX. Rather than creating a second kernel
virtual mapping, the existing mapping is updated using recently added
coco mechanisms. When memory is changed between private and shared using
set_memory_decrypted() and set_memory_encrypted(), the PTEs for the
existing kernel mapping are changed to add or remove the vTOM bit
in the guest physical address, just as with TDX. The hypercalls to
change the memory status on the host side are made using the existing
callback mechanism. Everything just works, with a minor tweak to map
the I/O APIC to use private accesses.
To accomplish the switch in approach, the following must be done in
in this single patch:
* Update Hyper-V initialization to set the cc _mask based on vTOM
and do other coco initialization.
* Update physical_mask so the vTOM bit is no longer treated as part
of the physical address
* Update cc_mkenc() and cc_mkdec() to be active for Hyper-V guests.
This makes the vTOM bit part of the protection flags.
* Code already exists to make hypercalls to inform Hyper-V about pages
changing between shared and private. Update this code to run as a
callback from __set_memory_enc_pgtable().
* Remove the Hyper-V special case from __set_memory_enc_dec(), and
make the normal case active for Hyper-V VMs, which have
CC_ATTR_GUEST_MEM_ENCRYPT, but not CC_ATTR_MEM_ENCRYPT.
[1] https://lore.kernel.org/all/[email protected]/
[2] https://lore.kernel.org/all/[email protected]/
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/coco/core.c | 10 ++++++++-
arch/x86/hyperv/ivm.c | 45 +++++++++++++++++++++++++++++++----------
arch/x86/include/asm/mshyperv.h | 8 ++------
arch/x86/kernel/cpu/mshyperv.c | 15 +++++++-------
arch/x86/mm/pat/set_memory.c | 6 ++----
5 files changed, 54 insertions(+), 30 deletions(-)
diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 49b44f8..de4e83e 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -78,7 +78,13 @@ static bool amd_cc_platform_has(enum cc_attr attr)
static bool hyperv_cc_platform_has(enum cc_attr attr)
{
- return attr == CC_ATTR_GUEST_MEM_ENCRYPT;
+ switch (attr) {
+ case CC_ATTR_GUEST_MEM_ENCRYPT:
+ case CC_ATTR_HAS_PARAVISOR:
+ return true;
+ default:
+ return false;
+ }
}
bool cc_platform_has(enum cc_attr attr)
@@ -108,6 +114,7 @@ u64 cc_mkenc(u64 val)
switch (vendor) {
case CC_VENDOR_AMD:
return val | cc_mask;
+ case CC_VENDOR_HYPERV:
case CC_VENDOR_INTEL:
return val & ~cc_mask;
default:
@@ -121,6 +128,7 @@ u64 cc_mkdec(u64 val)
switch (vendor) {
case CC_VENDOR_AMD:
return val & ~cc_mask;
+ case CC_VENDOR_HYPERV:
case CC_VENDOR_INTEL:
return val | cc_mask;
default:
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index e8be4c2..29ccbe8 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -13,6 +13,7 @@
#include <asm/svm.h>
#include <asm/sev.h>
#include <asm/io.h>
+#include <asm/coco.h>
#include <asm/mshyperv.h>
#include <asm/hypervisor.h>
@@ -233,7 +234,6 @@ void hv_ghcb_msr_read(u64 msr, u64 *value)
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(hv_ghcb_msr_read);
-#endif
/*
* hv_mark_gpa_visibility - Set pages visible to host via hvcall.
@@ -286,27 +286,25 @@ static int hv_mark_gpa_visibility(u16 count, const u64 pfn[],
}
/*
- * hv_set_mem_host_visibility - Set specified memory visible to host.
+ * hv_vtom_set_host_visibility - Set specified memory visible to host.
*
* In Isolation VM, all guest memory is encrypted from host and guest
* needs to set memory visible to host via hvcall before sharing memory
* with host. This function works as wrap of hv_mark_gpa_visibility()
* with memory base and size.
*/
-int hv_set_mem_host_visibility(unsigned long kbuffer, int pagecount, bool visible)
+static bool hv_vtom_set_host_visibility(unsigned long kbuffer, int pagecount, bool enc)
{
- enum hv_mem_host_visibility visibility = visible ?
- VMBUS_PAGE_VISIBLE_READ_WRITE : VMBUS_PAGE_NOT_VISIBLE;
+ enum hv_mem_host_visibility visibility = enc ?
+ VMBUS_PAGE_NOT_VISIBLE : VMBUS_PAGE_VISIBLE_READ_WRITE;
u64 *pfn_array;
int ret = 0;
+ bool result = true;
int i, pfn;
- if (!hv_is_isolation_supported() || !hv_hypercall_pg)
- return 0;
-
pfn_array = kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
if (!pfn_array)
- return -ENOMEM;
+ return false;
for (i = 0, pfn = 0; i < pagecount; i++) {
pfn_array[pfn] = virt_to_hvpfn((void *)kbuffer + i * HV_HYP_PAGE_SIZE);
@@ -315,17 +313,42 @@ int hv_set_mem_host_visibility(unsigned long kbuffer, int pagecount, bool visibl
if (pfn == HV_MAX_MODIFY_GPA_REP_COUNT || i == pagecount - 1) {
ret = hv_mark_gpa_visibility(pfn, pfn_array,
visibility);
- if (ret)
+ if (ret) {
+ result = false;
goto err_free_pfn_array;
+ }
pfn = 0;
}
}
err_free_pfn_array:
kfree(pfn_array);
- return ret;
+ return result;
+}
+
+static bool hv_vtom_tlb_flush_required(bool private)
+{
+ return true;
}
+static bool hv_vtom_cache_flush_required(void)
+{
+ return false;
+}
+
+void __init hv_vtom_init(void)
+{
+ cc_set_vendor(CC_VENDOR_HYPERV);
+ cc_set_mask(ms_hyperv.shared_gpa_boundary);
+ physical_mask &= ms_hyperv.shared_gpa_boundary - 1;
+
+ x86_platform.guest.enc_cache_flush_required = hv_vtom_cache_flush_required;
+ x86_platform.guest.enc_tlb_flush_required = hv_vtom_tlb_flush_required;
+ x86_platform.guest.enc_status_change_finish = hv_vtom_set_host_visibility;
+}
+
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+
/*
* hv_map_memory - map memory to extra space in the AMD SEV-SNP Isolation VM.
*/
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 61f0c20..59b3310 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -174,18 +174,19 @@ static inline void hv_apic_init(void) {}
int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
struct hv_interrupt_entry *entry);
int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry);
-int hv_set_mem_host_visibility(unsigned long addr, int numpages, bool visible);
#ifdef CONFIG_AMD_MEM_ENCRYPT
void hv_ghcb_msr_write(u64 msr, u64 value);
void hv_ghcb_msr_read(u64 msr, u64 *value);
bool hv_ghcb_negotiate_protocol(void);
void hv_ghcb_terminate(unsigned int set, unsigned int reason);
+void hv_vtom_init(void);
#else
static inline void hv_ghcb_msr_write(u64 msr, u64 value) {}
static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {}
static inline bool hv_ghcb_negotiate_protocol(void) { return false; }
static inline void hv_ghcb_terminate(unsigned int set, unsigned int reason) {}
+static inline void hv_vtom_init(void) {}
#endif
extern bool hv_isolation_type_snp(void);
@@ -241,11 +242,6 @@ static inline int hyperv_flush_guest_mapping_range(u64 as,
}
static inline void hv_set_register(unsigned int reg, u64 value) { }
static inline u64 hv_get_register(unsigned int reg) { return 0; }
-static inline int hv_set_mem_host_visibility(unsigned long addr, int numpages,
- bool visible)
-{
- return -1;
-}
#endif /* CONFIG_HYPERV */
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 8316139..b080795 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -33,7 +33,6 @@
#include <asm/nmi.h>
#include <clocksource/hyperv_timer.h>
#include <asm/numa.h>
-#include <asm/coco.h>
/* Is Linux running as the root partition? */
bool hv_root_partition;
@@ -325,8 +324,10 @@ static void __init ms_hyperv_init_platform(void)
if (ms_hyperv.priv_high & HV_ISOLATION) {
ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
- ms_hyperv.shared_gpa_boundary =
- BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
+
+ if (ms_hyperv.shared_gpa_boundary_active)
+ ms_hyperv.shared_gpa_boundary =
+ BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
@@ -337,11 +338,6 @@ static void __init ms_hyperv_init_platform(void)
swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary;
#endif
}
- /* Isolation VMs are unenlightened SEV-based VMs, thus this check: */
- if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
- if (hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE)
- cc_set_vendor(CC_VENDOR_HYPERV);
- }
}
if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
@@ -410,6 +406,9 @@ static void __init ms_hyperv_init_platform(void)
i8253_clear_counter_on_shutdown = false;
#if IS_ENABLED(CONFIG_HYPERV)
+ if ((hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS) ||
+ (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP))
+ hv_vtom_init();
/*
* Setup the hook to get control post apic initialization.
*/
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 97342c4..c8612f5 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2116,10 +2116,8 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
{
- if (hv_is_isolation_supported())
- return hv_set_mem_host_visibility(addr, numpages, !enc);
-
- if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
+ if (cc_platform_has(CC_ATTR_MEM_ENCRYPT) ||
+ cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
return __set_memory_enc_pgtable(addr, numpages, enc);
return 0;
--
1.8.3.1
With the vTOM bit now treated as a protection flag and not part of
the physical address, avoid remapping physical addresses with vTOM set
since technically such addresses aren't valid. Use ioremap_cache()
instead of memremap() to ensure that the mapping provides decrypted
access, which will correctly set the vTOM bit as a protection flag.
While this change is not required for correctness with the current
implementation of memremap(), for general code hygiene it's better to
not depend on the mapping functions doing something reasonable with
a physical address that is out-of-range.
While here, fix typos in two error messages.
Signed-off-by: Michael Kelley <[email protected]>
---
arch/x86/hyperv/hv_init.c | 7 +++++--
drivers/hv/hv.c | 23 +++++++++++++----------
2 files changed, 18 insertions(+), 12 deletions(-)
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 2977412..c881b5a 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -64,7 +64,10 @@ static int hyperv_init_ghcb(void)
* memory boundary and map it here.
*/
rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
- ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);
+
+ /* Mask out vTOM bit. ioremap_cache() maps decrypted */
+ ghcb_gpa &= ~ms_hyperv.shared_gpa_boundary;
+ ghcb_va = (void *)ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);
if (!ghcb_va)
return -ENOMEM;
@@ -220,7 +223,7 @@ static int hv_cpu_die(unsigned int cpu)
if (hv_ghcb_pg) {
ghcb_va = (void **)this_cpu_ptr(hv_ghcb_pg);
if (*ghcb_va)
- memunmap(*ghcb_va);
+ iounmap(*ghcb_va);
*ghcb_va = NULL;
}
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 4d6480d..410e6c4 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -217,11 +217,13 @@ void hv_synic_enable_regs(unsigned int cpu)
simp.simp_enabled = 1;
if (hv_isolation_type_snp()) {
+ /* Mask out vTOM bit. ioremap_cache() maps decrypted */
+ u64 base = (simp.base_simp_gpa << HV_HYP_PAGE_SHIFT) &
+ ~ms_hyperv.shared_gpa_boundary;
hv_cpu->synic_message_page
- = memremap(simp.base_simp_gpa << HV_HYP_PAGE_SHIFT,
- HV_HYP_PAGE_SIZE, MEMREMAP_WB);
+ = (void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
if (!hv_cpu->synic_message_page)
- pr_err("Fail to map syinc message page.\n");
+ pr_err("Fail to map synic message page.\n");
} else {
simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
>> HV_HYP_PAGE_SHIFT;
@@ -234,12 +236,13 @@ void hv_synic_enable_regs(unsigned int cpu)
siefp.siefp_enabled = 1;
if (hv_isolation_type_snp()) {
- hv_cpu->synic_event_page =
- memremap(siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT,
- HV_HYP_PAGE_SIZE, MEMREMAP_WB);
-
+ /* Mask out vTOM bit. ioremap_cache() maps decrypted */
+ u64 base = (siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT) &
+ ~ms_hyperv.shared_gpa_boundary;
+ hv_cpu->synic_event_page
+ = (void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
if (!hv_cpu->synic_event_page)
- pr_err("Fail to map syinc event page.\n");
+ pr_err("Fail to map synic event page.\n");
} else {
siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
>> HV_HYP_PAGE_SHIFT;
@@ -316,7 +319,7 @@ void hv_synic_disable_regs(unsigned int cpu)
*/
simp.simp_enabled = 0;
if (hv_isolation_type_snp())
- memunmap(hv_cpu->synic_message_page);
+ iounmap(hv_cpu->synic_message_page);
else
simp.base_simp_gpa = 0;
@@ -326,7 +329,7 @@ void hv_synic_disable_regs(unsigned int cpu)
siefp.siefp_enabled = 0;
if (hv_isolation_type_snp())
- memunmap(hv_cpu->synic_event_page);
+ iounmap(hv_cpu->synic_event_page);
else
siefp.base_siefp_gpa = 0;
--
1.8.3.1
With changes to how Hyper-V guest VMs flip memory between private
(encrypted) and shared (decrypted), creating a second kernel virtual
mapping for shared memory is no longer necessary. Everything needed
for the transition to shared is handled by set_memory_decrypted().
As such, remove the code to create and manage the second
mapping for VMBus monitor pages. Because set_memory_decrypted()
and set_memory_encrypted() are no-ops in normal VMs, it's
not even necessary to test for being in a Confidential VM
(a.k.a., "Isolation VM").
Signed-off-by: Michael Kelley <[email protected]>
---
drivers/hv/connection.c | 113 ++++++++++++----------------------------------
drivers/hv/hyperv_vmbus.h | 2 -
2 files changed, 28 insertions(+), 87 deletions(-)
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 9dc27e5..e473b69 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -104,8 +104,14 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
}
- msg->monitor_page1 = vmbus_connection.monitor_pages_pa[0];
- msg->monitor_page2 = vmbus_connection.monitor_pages_pa[1];
+ /*
+ * shared_gpa_boundary is zero in non-SNP VMs, so it's safe to always
+ * do the add
+ */
+ msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]) +
+ ms_hyperv.shared_gpa_boundary;
+ msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]) +
+ ms_hyperv.shared_gpa_boundary;
msg->target_vcpu = hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
@@ -219,72 +225,27 @@ int vmbus_connect(void)
* Setup the monitor notification facility. The 1st page for
* parent->child and the 2nd page for child->parent
*/
- vmbus_connection.monitor_pages[0] = (void *)hv_alloc_hyperv_zeroed_page();
- vmbus_connection.monitor_pages[1] = (void *)hv_alloc_hyperv_zeroed_page();
+ vmbus_connection.monitor_pages[0] = (void *)hv_alloc_hyperv_page();
+ vmbus_connection.monitor_pages[1] = (void *)hv_alloc_hyperv_page();
if ((vmbus_connection.monitor_pages[0] == NULL) ||
(vmbus_connection.monitor_pages[1] == NULL)) {
ret = -ENOMEM;
goto cleanup;
}
- vmbus_connection.monitor_pages_original[0]
- = vmbus_connection.monitor_pages[0];
- vmbus_connection.monitor_pages_original[1]
- = vmbus_connection.monitor_pages[1];
- vmbus_connection.monitor_pages_pa[0]
- = virt_to_phys(vmbus_connection.monitor_pages[0]);
- vmbus_connection.monitor_pages_pa[1]
- = virt_to_phys(vmbus_connection.monitor_pages[1]);
-
- if (hv_is_isolation_supported()) {
- ret = set_memory_decrypted((unsigned long)
- vmbus_connection.monitor_pages[0],
- 1);
- ret |= set_memory_decrypted((unsigned long)
- vmbus_connection.monitor_pages[1],
- 1);
- if (ret)
- goto cleanup;
-
- /*
- * Isolation VM with AMD SNP needs to access monitor page via
- * address space above shared gpa boundary.
- */
- if (hv_isolation_type_snp()) {
- vmbus_connection.monitor_pages_pa[0] +=
- ms_hyperv.shared_gpa_boundary;
- vmbus_connection.monitor_pages_pa[1] +=
- ms_hyperv.shared_gpa_boundary;
-
- vmbus_connection.monitor_pages[0]
- = memremap(vmbus_connection.monitor_pages_pa[0],
- HV_HYP_PAGE_SIZE,
- MEMREMAP_WB);
- if (!vmbus_connection.monitor_pages[0]) {
- ret = -ENOMEM;
- goto cleanup;
- }
-
- vmbus_connection.monitor_pages[1]
- = memremap(vmbus_connection.monitor_pages_pa[1],
- HV_HYP_PAGE_SIZE,
- MEMREMAP_WB);
- if (!vmbus_connection.monitor_pages[1]) {
- ret = -ENOMEM;
- goto cleanup;
- }
- }
-
- /*
- * Set memory host visibility hvcall smears memory
- * and so zero monitor pages here.
- */
- memset(vmbus_connection.monitor_pages[0], 0x00,
- HV_HYP_PAGE_SIZE);
- memset(vmbus_connection.monitor_pages[1], 0x00,
- HV_HYP_PAGE_SIZE);
+ ret = set_memory_decrypted((unsigned long)
+ vmbus_connection.monitor_pages[0], 1);
+ ret |= set_memory_decrypted((unsigned long)
+ vmbus_connection.monitor_pages[1], 1);
+ if (ret)
+ goto cleanup;
- }
+ /*
+ * Set_memory_decrypted() will change the memory contents if
+ * decryption occurs, so zero monitor pages here.
+ */
+ memset(vmbus_connection.monitor_pages[0], 0x00, HV_HYP_PAGE_SIZE);
+ memset(vmbus_connection.monitor_pages[1], 0x00, HV_HYP_PAGE_SIZE);
msginfo = kzalloc(sizeof(*msginfo) +
sizeof(struct vmbus_channel_initiate_contact),
@@ -376,31 +337,13 @@ void vmbus_disconnect(void)
vmbus_connection.int_page = NULL;
}
- if (hv_is_isolation_supported()) {
- /*
- * memunmap() checks input address is ioremap address or not
- * inside. It doesn't unmap any thing in the non-SNP CVM and
- * so not check CVM type here.
- */
- memunmap(vmbus_connection.monitor_pages[0]);
- memunmap(vmbus_connection.monitor_pages[1]);
-
- set_memory_encrypted((unsigned long)
- vmbus_connection.monitor_pages_original[0],
- 1);
- set_memory_encrypted((unsigned long)
- vmbus_connection.monitor_pages_original[1],
- 1);
- }
+ set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[0], 1);
+ set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[1], 1);
- hv_free_hyperv_page((unsigned long)
- vmbus_connection.monitor_pages_original[0]);
- hv_free_hyperv_page((unsigned long)
- vmbus_connection.monitor_pages_original[1]);
- vmbus_connection.monitor_pages_original[0] =
- vmbus_connection.monitor_pages[0] = NULL;
- vmbus_connection.monitor_pages_original[1] =
- vmbus_connection.monitor_pages[1] = NULL;
+ hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[0]);
+ hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[1]);
+ vmbus_connection.monitor_pages[0] = NULL;
+ vmbus_connection.monitor_pages[1] = NULL;
}
/*
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index dc673ed..167ac51 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -241,8 +241,6 @@ struct vmbus_connection {
* is child->parent notification
*/
struct hv_monitor_page *monitor_pages[2];
- void *monitor_pages_original[2];
- phys_addr_t monitor_pages_pa[2];
struct list_head chn_msg_list;
spinlock_t channelmsg_lock;
--
1.8.3.1
With changes to how Hyper-V guest VMs flip memory between private
(encrypted) and shared (decrypted), it's no longer necessary to
have separate code paths for mapping VMBus ring buffers for
for normal VMs and for Confidential VMs.
As such, remove the code path that uses vmap_pfn(), and set
the protection flags argument to vmap() to account for the
difference between normal and Confidential VMs.
Signed-off-by: Michael Kelley <[email protected]>
---
drivers/hv/ring_buffer.c | 62 ++++++++++++++++--------------------------------
1 file changed, 20 insertions(+), 42 deletions(-)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index b4a91b1..20a0631 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -186,8 +186,6 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
struct page *pages, u32 page_cnt, u32 max_pkt_size)
{
struct page **pages_wraparound;
- unsigned long *pfns_wraparound;
- u64 pfn;
int i;
BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
@@ -196,50 +194,30 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
* First page holds struct hv_ring_buffer, do wraparound mapping for
* the rest.
*/
- if (hv_isolation_type_snp()) {
- pfn = page_to_pfn(pages) +
- PFN_DOWN(ms_hyperv.shared_gpa_boundary);
+ pages_wraparound = kcalloc(page_cnt * 2 - 1,
+ sizeof(struct page *),
+ GFP_KERNEL);
+ if (!pages_wraparound)
+ return -ENOMEM;
- pfns_wraparound = kcalloc(page_cnt * 2 - 1,
- sizeof(unsigned long), GFP_KERNEL);
- if (!pfns_wraparound)
- return -ENOMEM;
-
- pfns_wraparound[0] = pfn;
- for (i = 0; i < 2 * (page_cnt - 1); i++)
- pfns_wraparound[i + 1] = pfn + i % (page_cnt - 1) + 1;
-
- ring_info->ring_buffer = (struct hv_ring_buffer *)
- vmap_pfn(pfns_wraparound, page_cnt * 2 - 1,
- pgprot_decrypted(PAGE_KERNEL_NOENC));
- kfree(pfns_wraparound);
-
- if (!ring_info->ring_buffer)
- return -ENOMEM;
-
- /* Zero ring buffer after setting memory host visibility. */
- memset(ring_info->ring_buffer, 0x00, PAGE_SIZE * page_cnt);
- } else {
- pages_wraparound = kcalloc(page_cnt * 2 - 1,
- sizeof(struct page *),
- GFP_KERNEL);
- if (!pages_wraparound)
- return -ENOMEM;
-
- pages_wraparound[0] = pages;
- for (i = 0; i < 2 * (page_cnt - 1); i++)
- pages_wraparound[i + 1] =
- &pages[i % (page_cnt - 1) + 1];
+ pages_wraparound[0] = pages;
+ for (i = 0; i < 2 * (page_cnt - 1); i++)
+ pages_wraparound[i + 1] =
+ &pages[i % (page_cnt - 1) + 1];
- ring_info->ring_buffer = (struct hv_ring_buffer *)
- vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
- PAGE_KERNEL);
+ ring_info->ring_buffer = (struct hv_ring_buffer *)
+ vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
+ pgprot_decrypted(PAGE_KERNEL_NOENC));
- kfree(pages_wraparound);
- if (!ring_info->ring_buffer)
- return -ENOMEM;
- }
+ kfree(pages_wraparound);
+ if (!ring_info->ring_buffer)
+ return -ENOMEM;
+ /*
+ * Ensure the header page is zero'ed since
+ * encryption status may have changed.
+ */
+ memset(ring_info->ring_buffer, 0, HV_HYP_PAGE_SIZE);
ring_info->ring_buffer->read_index =
ring_info->ring_buffer->write_index = 0;
--
1.8.3.1
On Thu, Oct 20, 2022 at 10:57:14AM -0700, Michael Kelley wrote:
> To support PCI pass-thru devices in Confidential VMs, Hyper-V
> has added hypercalls to read and write MMIO space. Add the
> appropriate definitions to hyperv-tlfs.h and implement
> functions to make the hypercalls. These functions are used
> in a subsequent patch.
>
> Co-developed-by: Dexuan Cui <[email protected]>
> Signed-off-by: Dexuan Cui <[email protected]>
> Signed-off-by: Michael Kelley <[email protected]>
> ---
> arch/x86/include/asm/hyperv-tlfs.h | 3 ++
> drivers/pci/controller/pci-hyperv.c | 62 +++++++++++++++++++++++++++++++++++++
> include/asm-generic/hyperv-tlfs.h | 22 +++++++++++++
> 3 files changed, 87 insertions(+)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 3089ec3..f769b9d 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -117,6 +117,9 @@
> /* Recommend using enlightened VMCS */
> #define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED BIT(14)
>
> +/* Use hypercalls for MMIO config space access */
> +#define HV_X64_USE_MMIO_HYPERCALLS BIT(21)
> +
> /*
> * CPU management features identification.
> * These are HYPERV_CPUID_CPU_MANAGEMENT_FEATURES.EAX bits.
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index e7c6f66..02ebf3e 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -1054,6 +1054,68 @@ static int wslot_to_devfn(u32 wslot)
> return PCI_DEVFN(slot_no.bits.dev, slot_no.bits.func);
> }
>
> +static void hv_pci_read_mmio(phys_addr_t gpa, int size, u32 *val)
> +{
> + struct hv_mmio_read_input *in;
> + struct hv_mmio_read_output *out;
> + u64 ret;
> +
> + /*
> + * Must be called with interrupts disabled so it is safe
> + * to use the per-cpu input argument page. Use it for
> + * both input and output.
> + */
> + in = *this_cpu_ptr(hyperv_pcpu_input_arg);
> + out = *this_cpu_ptr(hyperv_pcpu_input_arg) + sizeof(*in);
> + in->gpa = gpa;
> + in->size = size;
> +
> + ret = hv_do_hypercall(HVCALL_MMIO_READ, in, out);
> + if (hv_result_success(ret)) {
> + switch (size) {
> + case 1:
> + *val = *(u8 *)(out->data);
> + break;
> + case 2:
> + *val = *(u16 *)(out->data);
> + break;
> + default:
> + *val = *(u32 *)(out->data);
> + break;
> + }
> + } else
> + pr_err("MMIO read hypercall failed with status %llx\n", ret);
Too bad there's not more information to give the user/administrator
here. Seeing "MMIO read hypercall failed with status -5" in the log
doesn't give many clues about where to look or who to notify. I don't
know what's even feasible, but driver name, device, address (gpa),
size would all be possibilities.
Bjorn
From: Bjorn Helgaas <[email protected]> Sent: Thursday, October 20, 2022 12:04 PM
>
> On Thu, Oct 20, 2022 at 10:57:14AM -0700, Michael Kelley wrote:
> > To support PCI pass-thru devices in Confidential VMs, Hyper-V
> > has added hypercalls to read and write MMIO space. Add the
> > appropriate definitions to hyperv-tlfs.h and implement
> > functions to make the hypercalls. These functions are used
> > in a subsequent patch.
> >
> > Co-developed-by: Dexuan Cui <[email protected]>
> > Signed-off-by: Dexuan Cui <[email protected]>
> > Signed-off-by: Michael Kelley <[email protected]>
> > ---
> > arch/x86/include/asm/hyperv-tlfs.h | 3 ++
> > drivers/pci/controller/pci-hyperv.c | 62
> +++++++++++++++++++++++++++++++++++++
> > include/asm-generic/hyperv-tlfs.h | 22 +++++++++++++
> > 3 files changed, 87 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-
> tlfs.h
> > index 3089ec3..f769b9d 100644
> > --- a/arch/x86/include/asm/hyperv-tlfs.h
> > +++ b/arch/x86/include/asm/hyperv-tlfs.h
> > @@ -117,6 +117,9 @@
> > /* Recommend using enlightened VMCS */
> > #define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED BIT(14)
> >
> > +/* Use hypercalls for MMIO config space access */
> > +#define HV_X64_USE_MMIO_HYPERCALLS BIT(21)
> > +
> > /*
> > * CPU management features identification.
> > * These are HYPERV_CPUID_CPU_MANAGEMENT_FEATURES.EAX bits.
> > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> > index e7c6f66..02ebf3e 100644
> > --- a/drivers/pci/controller/pci-hyperv.c
> > +++ b/drivers/pci/controller/pci-hyperv.c
> > @@ -1054,6 +1054,68 @@ static int wslot_to_devfn(u32 wslot)
> > return PCI_DEVFN(slot_no.bits.dev, slot_no.bits.func);
> > }
> >
> > +static void hv_pci_read_mmio(phys_addr_t gpa, int size, u32 *val)
> > +{
> > + struct hv_mmio_read_input *in;
> > + struct hv_mmio_read_output *out;
> > + u64 ret;
> > +
> > + /*
> > + * Must be called with interrupts disabled so it is safe
> > + * to use the per-cpu input argument page. Use it for
> > + * both input and output.
> > + */
> > + in = *this_cpu_ptr(hyperv_pcpu_input_arg);
> > + out = *this_cpu_ptr(hyperv_pcpu_input_arg) + sizeof(*in);
> > + in->gpa = gpa;
> > + in->size = size;
> > +
> > + ret = hv_do_hypercall(HVCALL_MMIO_READ, in, out);
> > + if (hv_result_success(ret)) {
> > + switch (size) {
> > + case 1:
> > + *val = *(u8 *)(out->data);
> > + break;
> > + case 2:
> > + *val = *(u16 *)(out->data);
> > + break;
> > + default:
> > + *val = *(u32 *)(out->data);
> > + break;
> > + }
> > + } else
> > + pr_err("MMIO read hypercall failed with status %llx\n", ret);
>
> Too bad there's not more information to give the user/administrator
> here. Seeing "MMIO read hypercall failed with status -5" in the log
> doesn't give many clues about where to look or who to notify. I don't
> know what's even feasible, but driver name, device, address (gpa),
> size would all be possibilities.
>
Good point. We can pass the device as an input argument to hv_pci_read_mmio()
and hv_pci_write_mmio(), use dev_err() instead of pr_err(), and provide the
gpa and size in the message. This is one of those errors that should never
happen, but when it does, having the additional info will be helpful for
debugging. I'll do this in v2.
Michael
On Thu, Oct 20, 2022 at 10:57:05AM -0700, Michael Kelley wrote:
> Current code always maps the IOAPIC as shared (decrypted) in a
> confidential VM. But Hyper-V guest VMs on AMD SEV-SNP with vTOM
> enabled use a paravisor running in VMPL0 to emulate the IOAPIC.
> In such a case, the IOAPIC must be accessed as private (encrypted).
>
> Fix this by gating the IOAPIC decrypted mapping on a new
> cc_platform_has() attribute that a subsequent patch in the series
> will set only for Hyper-V guests. The new attribute is named
> somewhat generically because similar paravisor emulation cases
> may arise in the future.
>
> Signed-off-by: Michael Kelley <[email protected]>
Reviewed-by: Wei Liu <[email protected]>
> ---
> arch/x86/kernel/apic/io_apic.c | 3 ++-
> include/linux/cc_platform.h | 13 +++++++++++++
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index a868b76..d2c1bf7 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -2686,7 +2686,8 @@ static void io_apic_set_fixmap(enum fixed_addresses idx, phys_addr_t phys)
> * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot
> * bits, just like normal ioremap():
> */
> - flags = pgprot_decrypted(flags);
> + if (!cc_platform_has(CC_ATTR_HAS_PARAVISOR))
> + flags = pgprot_decrypted(flags);
>
> __set_fixmap(idx, phys, flags);
> }
> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> index cb0d6cd..b6c4a79 100644
> --- a/include/linux/cc_platform.h
> +++ b/include/linux/cc_platform.h
> @@ -90,6 +90,19 @@ enum cc_attr {
> * Examples include TDX Guest.
> */
> CC_ATTR_HOTPLUG_DISABLED,
> +
> + /**
> + * @CC_ATTR_HAS_PARAVISOR: Guest VM is running with a paravisor
> + *
> + * The platform/OS is running as a guest/virtual machine with
> + * a paravisor in VMPL0. Having a paravisor affects things
> + * like whether the I/O APIC is emulated and operates in the
> + * encrypted or decrypted portion of the guest physical address
> + * space.
> + *
> + * Examples include Hyper-V SEV-SNP guests using vTOM.
> + */
> + CC_ATTR_HAS_PARAVISOR,
> };
>
> #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> --
> 1.8.3.1
>
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> Reorder some code as preparation for a subsequent patch. No
> functional change.
>
> Signed-off-by: Michael Kelley <[email protected]>
Reviewed-by: Tianyu Lan <[email protected]>
> ---
> arch/x86/hyperv/ivm.c | 68 +++++++++++++++++++++++++--------------------------
> 1 file changed, 34 insertions(+), 34 deletions(-)
>
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index 1dbcbd9..f33c67e 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -235,40 +235,6 @@ void hv_ghcb_msr_read(u64 msr, u64 *value)
> EXPORT_SYMBOL_GPL(hv_ghcb_msr_read);
> #endif
>
> -enum hv_isolation_type hv_get_isolation_type(void)
> -{
> - if (!(ms_hyperv.priv_high & HV_ISOLATION))
> - return HV_ISOLATION_TYPE_NONE;
> - return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
> -}
> -EXPORT_SYMBOL_GPL(hv_get_isolation_type);
> -
> -/*
> - * hv_is_isolation_supported - Check system runs in the Hyper-V
> - * isolation VM.
> - */
> -bool hv_is_isolation_supported(void)
> -{
> - if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
> - return false;
> -
> - if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
> - return false;
> -
> - return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
> -}
> -
> -DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
> -
> -/*
> - * hv_isolation_type_snp - Check system runs in the AMD SEV-SNP based
> - * isolation VM.
> - */
> -bool hv_isolation_type_snp(void)
> -{
> - return static_branch_unlikely(&isolation_type_snp);
> -}
> -
> /*
> * hv_mark_gpa_visibility - Set pages visible to host via hvcall.
> *
> @@ -387,3 +353,37 @@ void hv_unmap_memory(void *addr)
> {
> vunmap(addr);
> }
> +
> +enum hv_isolation_type hv_get_isolation_type(void)
> +{
> + if (!(ms_hyperv.priv_high & HV_ISOLATION))
> + return HV_ISOLATION_TYPE_NONE;
> + return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
> +}
> +EXPORT_SYMBOL_GPL(hv_get_isolation_type);
> +
> +/*
> + * hv_is_isolation_supported - Check system runs in the Hyper-V
> + * isolation VM.
> + */
> +bool hv_is_isolation_supported(void)
> +{
> + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
> + return false;
> +
> + if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
> + return false;
> +
> + return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
> +}
> +
> +DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
> +
> +/*
> + * hv_isolation_type_snp - Check system runs in the AMD SEV-SNP based
> + * isolation VM.
> + */
> +bool hv_isolation_type_snp(void)
> +{
> + return static_branch_unlikely(&isolation_type_snp);
> +}
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> +
> +void __init hv_vtom_init(void)
> +{
> + cc_set_vendor(CC_VENDOR_HYPERV);
> + cc_set_mask(ms_hyperv.shared_gpa_boundary);
> + physical_mask &= ms_hyperv.shared_gpa_boundary - 1;
hv_vtom_init() also works for VBS case. VBS doesn't have vTOM support
and so shared_gpa_boundary should not be applied for VBS. Here seems to
assume ms_hyperv.shared_gpa_boundary to 0 for VBS, right?
From: Tianyu Lan <[email protected]> Sent: Thursday, November 3, 2022 7:01 AM
>
> On 10/21/2022 1:57 AM, Michael Kelley wrote:
> > +
> > +void __init hv_vtom_init(void)
> > +{
> > + cc_set_vendor(CC_VENDOR_HYPERV);
> > + cc_set_mask(ms_hyperv.shared_gpa_boundary);
> > + physical_mask &= ms_hyperv.shared_gpa_boundary - 1;
>
>
> hv_vtom_init() also works for VBS case. VBS doesn't have vTOM support
> and so shared_gpa_boundary should not be applied for VBS. Here seems to
> assume ms_hyperv.shared_gpa_boundary to 0 for VBS, right?
Yes, that is correct. In fact, you'll notice that this patch slightly changes
the code in ms_hyperv_init_platform() so that shared_gpa_boundary is
set only when it is known to be valid; otherwise it is left as zero. This
change is specifically so that shared_gpa_boundary is zero for the VBS
case.
Michael
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> With changes to how Hyper-V guest VMs flip memory between private
> (encrypted) and shared (decrypted), creating a second kernel virtual
> mapping for shared memory is no longer necessary. Everything needed
> for the transition to shared is handled by set_memory_decrypted().
>
> As such, remove the code to create and manage the second
> mapping for VMBus monitor pages. Because set_memory_decrypted()
> and set_memory_encrypted() are no-ops in normal VMs, it's
> not even necessary to test for being in a Confidential VM
> (a.k.a., "Isolation VM").
>
> Signed-off-by: Michael Kelley<[email protected]>
Reviewed-by: Tianyu Lan <[email protected]>
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> With changes to how Hyper-V guest VMs flip memory between private
> (encrypted) and shared (decrypted), creating a second kernel virtual
> mapping for shared memory is no longer necessary. Everything needed
> for the transition to shared is handled by set_memory_decrypted().
>
> As such, remove the code to create and manage the second
> mapping for the pre-allocated send and recv buffers. This mapping
> is the last user of hv_map_memory()/hv_unmap_memory(), so delete
> these functions as well. Finally, hv_map_memory() is the last
> user of vmap_pfn() in Hyper-V guest code, so remove the Kconfig
> selection of VMAP_PFN.
>
> Signed-off-by: Michael Kelley<[email protected]>
> ---
Reviewed-by: Tianyu Lan <[email protected]>
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> With changes to how Hyper-V guest VMs flip memory between private
> (encrypted) and shared (decrypted), it's no longer necessary to
> have separate code paths for mapping VMBus ring buffers for
> for normal VMs and for Confidential VMs.
>
> As such, remove the code path that uses vmap_pfn(), and set
> the protection flags argument to vmap() to account for the
> difference between normal and Confidential VMs.
>
> Signed-off-by: Michael Kelley<[email protected]>
> ---
Reviewed-by: Tianyu Lan <[email protected]>
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> With the vTOM bit now treated as a protection flag and not part of
> the physical address, avoid remapping physical addresses with vTOM set
> since technically such addresses aren't valid. Use ioremap_cache()
> instead of memremap() to ensure that the mapping provides decrypted
> access, which will correctly set the vTOM bit as a protection flag.
>
> While this change is not required for correctness with the current
> implementation of memremap(), for general code hygiene it's better to
> not depend on the mapping functions doing something reasonable with
> a physical address that is out-of-range.
>
> While here, fix typos in two error messages.
>
> Signed-off-by: Michael Kelley<[email protected]>
> ---
Reviewed-by: Tianyu Lan <[email protected]>
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> With changes to how Hyper-V guest VMs flip memory between private
> (encrypted) and shared (decrypted), creating a second kernel virtual
> mapping for shared memory is no longer necessary. Everything needed
> for the transition to shared is handled by set_memory_decrypted().
>
> As such, remove the code to create and manage the second
> mapping for the pre-allocated send and recv buffers. This mapping
> is the last user of hv_map_memory()/hv_unmap_memory(), so delete
> these functions as well. Finally, hv_map_memory() is the last
> user of vmap_pfn() in Hyper-V guest code, so remove the Kconfig
> selection of VMAP_PFN.
>
> Signed-off-by: Michael Kelley<[email protected]>
Reviewed-by: Tianyu Lan <[email protected]>
On 10/21/2022 1:57 AM, Michael Kelley wrote:
> Hyper-V guests on AMD SEV-SNP hardware have the option of using the
> "virtual Top Of Memory" (vTOM) feature specified by the SEV-SNP
> architecture. With vTOM, shared vs. private memory accesses are
> controlled by splitting the guest physical address space into two
> halves. vTOM is the dividing line where the uppermost bit of the
> physical address space is set; e.g., with 47 bits of guest physical
> address space, vTOM is 0x40000000000 (bit 46 is set). Guest phyiscal
> memory is accessible at two parallel physical addresses -- one below
> vTOM and one above vTOM. Accesses below vTOM are private (encrypted)
> while accesses above vTOM are shared (decrypted). In this sense, vTOM
> is like the GPA.SHARED bit in Intel TDX.
>
> Support for Hyper-V guests using vTOM was added to the Linux kernel in
> two patch sets[1][2]. This support treats the vTOM bit as part of
> the physical address. For accessing shared (decrypted) memory, these
> patch sets create a second kernel virtual mapping that maps to physical
> addresses above vTOM.
>
> A better approach is to treat the vTOM bit as a protection flag, not
> as part of the physical address. This new approach is like the approach
> for the GPA.SHARED bit in Intel TDX. Rather than creating a second kernel
> virtual mapping, the existing mapping is updated using recently added
> coco mechanisms. When memory is changed between private and shared using
> set_memory_decrypted() and set_memory_encrypted(), the PTEs for the
> existing kernel mapping are changed to add or remove the vTOM bit
> in the guest physical address, just as with TDX. The hypercalls to
> change the memory status on the host side are made using the existing
> callback mechanism. Everything just works, with a minor tweak to map
> the I/O APIC to use private accesses.
>
> To accomplish the switch in approach, the following must be done in
> in this single patch:
>
> * Update Hyper-V initialization to set the cc _mask based on vTOM
> and do other coco initialization.
>
> * Update physical_mask so the vTOM bit is no longer treated as part
> of the physical address
>
> * Update cc_mkenc() and cc_mkdec() to be active for Hyper-V guests.
> This makes the vTOM bit part of the protection flags.
>
> * Code already exists to make hypercalls to inform Hyper-V about pages
> changing between shared and private. Update this code to run as a
> callback from __set_memory_enc_pgtable().
>
> * Remove the Hyper-V special case from __set_memory_enc_dec(), and
> make the normal case active for Hyper-V VMs, which have
> CC_ATTR_GUEST_MEM_ENCRYPT, but not CC_ATTR_MEM_ENCRYPT.
>
> [1]https://lore.kernel.org/all/[email protected]/
> [2]https://lore.kernel.org/all/[email protected]/
>
> Signed-off-by: Michael Kelley<[email protected]>
> ---
Reviewed-by: Tianyu Lan <[email protected]>