Previously, when a protected VM was rebooted or when it was shut down,
its memory was made unprotected, and then the protected VM itself was
destroyed. Looping over the whole address space can take some time,
considering the overhead of the various Ultravisor Calls (UVCs). This
means that a reboot or a shutdown would take a potentially long amount
of time, depending on the amount of used memory.
This patchseries implements a deferred destroy mechanism for protected
guests. When a protected guest is destroyed, its memory can be cleared
in background, allowing the guest to restart or terminate significantly
faster than before.
There are 2 possibilities when a protected VM is torn down:
* it still has an address space associated (reboot case)
* it does not have an address space anymore (shutdown case)
For the reboot case, two new commands are available for the
KVM_S390_PV_COMMAND:
KVM_PV_ASYNC_DISABLE_PREPARE: prepares the current protected VM for
asynchronous teardown. The current VM will then continue immediately
as non-protected. If a protected VM had already been set aside without
starting the teardown process, this call will fail. In this case the
userspace process should issue a normal KVM_PV_DISABLE
KVM_PV_ASYNC_DISABLE: tears down the protected VM previously set aside
for asychronous teardown. This PV command should ideally be issued by
userspace from a separate thread. If a fatal signal is received (or
the process terminates naturally), the command will terminate
immediately without completing.
The idea is that userspace should first issue the
KVM_PV_ASYNC_DISABLE_PREPARE command, and in case of success, create a
new thread and issue KVM_PV_ASYNC_DISABLE from there. This also allows
for proper accounting of the CPU time needed for the asynchronous
teardown.
This means that the same address space can have memory belonging to
more than one protected guest, although only one will be running, the
others will in fact not even have any CPUs.
The shutdown case should be dealt with in userspace (e.g. using
clone(CLONE_VM)).
A module parameter is also provided to disable the new functionality,
which is otherwise enabled by default. This should not be an issue
since the new functionality is opt-in anyway. This is mainly thought to
aid debugging.
v6->v7
* moved INIT_LIST_HEAD inside spinlock in patch 1
* improved commit messages in patch 2
* added missing locks in patch 3
* added and expanded some comments in patch 11
* rebased
v5->v6
* completely reworked the series
* removed kernel thread for asynchronous teardown
* added new commands to KVM_S390_PV_COMMAND ioctl
v4->v5
* fixed and improved some patch descriptions
* added some comments to better explain what's going on
* use vma_lookup instead of find_vma
* rename is_protected to protected_count since now it's used as a counter
v3->v4
* added patch 2
* split patch 3
* removed the shutdown part -- will be a separate patchseries
* moved the patch introducing the module parameter
v2->v3
* added definitions for CC return codes for the UVC instruction
* improved make_secure_pte:
- renamed rc to cc
- added comments to explain why returning -EAGAIN is ok
* fixed kvm_s390_pv_replace_asce and kvm_s390_pv_remove_old_asce:
- renamed
- added locking
- moved to gmap.c
* do proper error management in do_secure_storage_access instead of
trying again hoping to get a different exception
* fix outdated patch descriptions
v1->v2
* rebased on a more recent kernel
* improved/expanded some patch descriptions
* improves/expanded some comments
* added patch 1, which prevents stall notification when the system is
under heavy load.
* rename some members of struct deferred_priv to improve readability
* avoid an use-after-free bug of the struct mm in case of shutdown
* add missing return when lazy destroy is disabled
* add support for OOM notifier
Claudio Imbrenda (17):
KVM: s390: pv: leak the topmost page table when destroy fails
KVM: s390: pv: handle secure storage violations for protected guests
KVM: s390: pv: handle secure storage exceptions for normal guests
KVM: s390: pv: refactor s390_reset_acc
KVM: s390: pv: usage counter instead of flag
KVM: s390: pv: add export before import
KVM: s390: pv: module parameter to fence lazy destroy
KVM: s390: pv: make kvm_s390_cpus_from_pv global
KVM: s390: pv: clear the state without memset
KVM: s390: pv: add mmu_notifier
s390/mm: KVM: pv: when tearing down, try to destroy protected pages
KVM: s390: pv: refactoring of kvm_s390_pv_deinit_vm
KVM: s390: pv: cleanup leftover protected VMs if needed
KVM: s390: pv: asynchronous destroy for reboot
KVM: s390: pv: api documentation for asynchronous destroy
KVM: s390: pv: add KVM_CAP_S390_PROT_REBOOT_ASYNC
KVM: s390: pv: avoid export before import if possible
Documentation/virt/kvm/api.rst | 21 ++-
arch/s390/include/asm/gmap.h | 38 +++-
arch/s390/include/asm/kvm_host.h | 4 +
arch/s390/include/asm/mmu.h | 2 +-
arch/s390/include/asm/mmu_context.h | 2 +-
arch/s390/include/asm/pgtable.h | 20 ++-
arch/s390/include/asm/uv.h | 1 +
arch/s390/kernel/uv.c | 64 +++++++
arch/s390/kvm/kvm-s390.c | 59 ++++++-
arch/s390/kvm/kvm-s390.h | 3 +
arch/s390/kvm/pv.c | 259 ++++++++++++++++++++++++++--
arch/s390/mm/fault.c | 22 ++-
arch/s390/mm/gmap.c | 156 ++++++++++++++---
include/uapi/linux/kvm.h | 3 +
14 files changed, 606 insertions(+), 48 deletions(-)
--
2.34.1
If the appropriate UV feature bit is set, there is no need to perform
an export before import.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/kernel/uv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index e358b8bd864b..43393568f844 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -236,7 +236,8 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
{
- return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+ return !test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications) &&
+ uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
atomic_read(&mm->context.protected_count) > 1;
}
--
2.34.1
Add the module parameter "lazy_destroy", to allow the asynchronous destroy
mechanism to be switched off. This might be useful for debugging purposes.
The parameter is enabled by default.
Signed-off-by: Claudio Imbrenda <[email protected]>
Reviewed-by: Janosch Frank <[email protected]>
---
arch/s390/kvm/kvm-s390.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 577f1ead6a51..1a788f45d691 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -207,6 +207,11 @@ unsigned int diag9c_forwarding_hz;
module_param(diag9c_forwarding_hz, uint, 0644);
MODULE_PARM_DESC(diag9c_forwarding_hz, "Maximum diag9c forwarding per second, 0 to turn off");
+/* allow asynchronous deinit for protected guests */
+static int lazy_destroy = 1;
+module_param(lazy_destroy, int, 0444);
+MODULE_PARM_DESC(lazy_destroy, "Asynchronous destroy for protected guests");
+
/*
* For now we handle at most 16 double words as this is what the s390 base
* kernel handles and stores in the prefix page. If we ever need to go beyond
--
2.34.1
Due to upcoming changes, it will be possible to temporarily have
multiple protected VMs in the same address space, although only one
will be actually active.
In that scenario, it is necessary to perform an export of every page
that is to be imported, since the hardware does not allow a page
belonging to a protected guest to be imported into a different
protected guest.
This also applies to pages that are shared, and thus accessible by the
host.
Signed-off-by: Claudio Imbrenda <[email protected]>
Reviewed-by: Janosch Frank <[email protected]>
---
arch/s390/kernel/uv.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 2754471cc789..e358b8bd864b 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -234,6 +234,12 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
return uvcb->rc == 0x10a ? -ENXIO : -EINVAL;
}
+static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
+{
+ return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+ atomic_read(&mm->context.protected_count) > 1;
+}
+
/*
* Requests the Ultravisor to make a page accessible to a guest.
* If it's brought in the first time, it will be cleared. If
@@ -277,6 +283,8 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
lock_page(page);
ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
+ if (should_export_before_import(uvcb, gmap->mm))
+ uv_convert_from_secure(page_to_phys(page));
rc = make_secure_pte(ptep, uaddr, page, uvcb);
pte_unmap_unlock(ptep, ptelock);
unlock_page(page);
--
2.34.1
Add documentation for the new commands added to the KVM_S390_PV_COMMAND
ioctl.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
Documentation/virt/kvm/api.rst | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a4267104db50..3b9068aceead 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5010,11 +5010,13 @@ KVM_PV_ENABLE
===== =============================
KVM_PV_DISABLE
-
Deregister the VM from the Ultravisor and reclaim the memory that
had been donated to the Ultravisor, making it usable by the kernel
- again. All registered VCPUs are converted back to non-protected
- ones.
+ again. All registered VCPUs are converted back to non-protected
+ ones. If a previous VM had been prepared for asynchonous teardown
+ with KVM_PV_ASYNC_DISABLE_PREPARE and not actually torn down with
+ KVM_PV_ASYNC_DISABLE, it will be torn down in this call together with
+ the current VM.
KVM_PV_VM_SET_SEC_PARMS
Pass the image header from VM memory to the Ultravisor in
@@ -5027,6 +5029,19 @@ KVM_PV_VM_VERIFY
Verify the integrity of the unpacked image. Only if this succeeds,
KVM is allowed to start protected VCPUs.
+KVM_PV_ASYNC_DISABLE_PREPARE
+ Prepare the current protected VM for asynchronous teardown. The current
+ VM will then continue immediately as non-protected. If a protected VM had
+ already been set aside without starting the teardown process, this call
+ will fail. In this case the userspace process should issue a normal
+ KVM_PV_DISABLE.
+
+KVM_PV_ASYNC_DISABLE
+ Tear down the protected VM previously set aside for asynchronous teardown.
+ This PV command should ideally be issued by userspace from a separate
+ thread. If a fatal signal is received (or the process terminates
+ naturally), the command will terminate immediately without completing.
+
4.126 KVM_X86_SET_MSR_FILTER
----------------------------
--
2.34.1
The functions kvm_s390_cpus_from_pv needs to be called from pv.c, so
make it global.
Take the opportunity to add documentation.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/kvm/kvm-s390.c | 26 +++++++++++++++++++++++++-
arch/s390/kvm/kvm-s390.h | 1 +
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 1a788f45d691..0fc8d1aec396 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2175,7 +2175,20 @@ static int kvm_s390_set_cmma_bits(struct kvm *kvm,
return r;
}
-static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
+/**
+ * kvm_s390_cpus_from_pv - Convert all protected vCPUs in a protected VM to
+ * non protected.
+ * @kvm the VM whose protected vCPUs are to be converted
+ * @rcp return value for the RC field of the UVC (in case of error)
+ * @rrcp return value for the RRC field of the UVC (in case of error)
+ *
+ * Does not stop in case of error, tries to convert as many
+ * CPUs as possible. In case of error, the RC and RRC of the last error are
+ * returned.
+ *
+ * Return: 0 in case of success, otherwise -EIO
+ */
+int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
{
struct kvm_vcpu *vcpu;
u16 rc, rrc;
@@ -2202,6 +2215,17 @@ static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
return ret;
}
+/**
+ * kvm_s390_cpus_to_pv - Convert all non-protected vCPUs in a protected VM
+ * to protected.
+ * @kvm the VM whose protected vCPUs are to be converted
+ * @rcp return value for the RC field of the UVC (in case of error)
+ * @rrcp return value for the RRC field of the UVC (in case of error)
+ *
+ * Tries to undo the conversion in case of error.
+ *
+ * Return: 0 in case of success, otherwise -EIO
+ */
static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
{
unsigned long i;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 098831e815e6..9276d910631b 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -365,6 +365,7 @@ int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu);
void kvm_s390_set_cpu_timer(struct kvm_vcpu *vcpu, __u64 cputm);
__u64 kvm_s390_get_cpu_timer(struct kvm_vcpu *vcpu);
+int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp);
/* implemented in diag.c */
int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);
--
2.34.1
Each secure guest must have a unique ASCE (address space control
element); we must avoid that new guests use the same page for their
ASCE, to avoid errors.
Since the ASCE mostly consists of the address of the topmost page table
(plus some flags), we must not return that memory to the pool unless
the ASCE is no longer in use.
Only a successful Destroy Secure Configuration UVC will make the ASCE
reusable again.
If the Destroy Configuration UVC fails, the ASCE cannot be reused for a
secure guest (either for the ASCE or for other memory areas). To avoid
a collision, it must not be used again. This is a permanent error and
the page becomes in practice unusable, so we set it aside and leak it.
On failure we already leak other memory that belongs to the ultravisor
(i.e. the variable and base storage for a guest) and not leaking the
topmost page table was an oversight.
This error (and thus the leakage) should not happen unless the hardware
is broken or KVM has some unknown serious bug.
Signed-off-by: Claudio Imbrenda <[email protected]>
Fixes: 29b40f105ec8d55 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
---
arch/s390/include/asm/gmap.h | 2 ++
arch/s390/kvm/pv.c | 9 +++--
arch/s390/mm/gmap.c | 69 ++++++++++++++++++++++++++++++++++++
3 files changed, 77 insertions(+), 3 deletions(-)
diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index 40264f60b0da..746e18bf8984 100644
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
unsigned long gaddr, unsigned long vmaddr);
int gmap_mark_unmergeable(void);
void s390_reset_acc(struct mm_struct *mm);
+void s390_remove_old_asce(struct gmap *gmap);
+int s390_replace_asce(struct gmap *gmap);
#endif /* _ASM_S390_GMAP_H */
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 7f7c0d6af2ce..3c59ef763dde 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -166,10 +166,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
atomic_set(&kvm->mm->context.is_protected, 0);
KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
- /* Inteded memory leak on "impossible" error */
- if (!cc)
+ /* Intended memory leak on "impossible" error */
+ if (!cc) {
kvm_s390_pv_dealloc_vm(kvm);
- return cc ? -EIO : 0;
+ return 0;
+ }
+ s390_replace_asce(kvm->arch.gmap);
+ return -EIO;
}
int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index dfee0ebb2fac..ce6cac4463f2 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2714,3 +2714,72 @@ void s390_reset_acc(struct mm_struct *mm)
mmput(mm);
}
EXPORT_SYMBOL_GPL(s390_reset_acc);
+
+/**
+ * s390_remove_old_asce - Remove the topmost level of page tables from the
+ * list of page tables of the gmap.
+ * @gmap the gmap whose table is to be removed
+ *
+ * This means that it will not be freed when the VM is torn down, and needs
+ * to be handled separately by the caller, unless an intentional leak is
+ * intended.
+ */
+void s390_remove_old_asce(struct gmap *gmap)
+{
+ struct page *old;
+
+ old = virt_to_page(gmap->table);
+ spin_lock(&gmap->guest_table_lock);
+ list_del(&old->lru);
+ /*
+ * in case the ASCE needs to be "removed" multiple times, for example
+ * if the VM is rebooted into secure mode several times
+ * concurrently.
+ */
+ INIT_LIST_HEAD(&old->lru);
+ spin_unlock(&gmap->guest_table_lock);
+}
+EXPORT_SYMBOL_GPL(s390_remove_old_asce);
+
+/**
+ * s390_replace_asce - Try to replace the current ASCE of a gmap with
+ * another equivalent one.
+ * @gmap the gmap
+ *
+ * If the allocation of the new top level page table fails, the ASCE is not
+ * replaced.
+ * In any case, the old ASCE is always removed from the list. Therefore the
+ * caller has to make sure to save a pointer to it beforehands, unless an
+ * intentional leak is intended.
+ */
+int s390_replace_asce(struct gmap *gmap)
+{
+ unsigned long asce;
+ struct page *page;
+ void *table;
+
+ s390_remove_old_asce(gmap);
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
+ if (!page)
+ return -ENOMEM;
+ table = page_to_virt(page);
+ memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
+
+ /*
+ * The caller has to deal with the old ASCE, but here we make sure
+ * the new one is properly added to the list of page tables, so that
+ * it will be freed when the VM is torn down.
+ */
+ spin_lock(&gmap->guest_table_lock);
+ list_add(&page->lru, &gmap->crst_list);
+ spin_unlock(&gmap->guest_table_lock);
+
+ asce = (gmap->asce & ~PAGE_MASK) | __pa(table);
+ WRITE_ONCE(gmap->asce, asce);
+ WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
+ WRITE_ONCE(gmap->table, table);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(s390_replace_asce);
--
2.34.1
Until now, destroying a protected guest was an entirely synchronous
operation that could potentially take a very long time, depending on
the size of the guest, due to the time needed to clean up the address
space from protected pages.
This patch implements an asynchronous destroy mechanism, that allows a
protected guest to reboot significantly faster than previously.
This is achieved by clearing the pages of the old guest in background.
In case of reboot, the new guest will be able to run in the same
address space almost immediately.
The old protected guest is then only destroyed when all of its memory has
been destroyed or otherwise made non protected.
Two new PV commands are added for the KVM_S390_PV_COMMAND ioctl:
KVM_PV_ASYNC_DISABLE_PREPARE: prepares the current protected VM for
asynchronous teardown. The current VM will then continue immediately
as non-protected. If a protected VM had already been set aside without
starting the teardown process, this call will fail.
KVM_PV_ASYNC_DISABLE: tears down the protected VM previously set aside
for asynchronous teardown. This PV command should ideally be issued by
userspace from a separate thread. If a fatal signal is received (or the
process terminates naturally), the command will terminate immediately
without completing.
Leftover protected VMs are cleaned up when a KVM VM is torn down
normally (either via IOCTL or when the process terminates); this
cleanup has been implemented in a previous patch.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/kvm/kvm-s390.c | 24 ++++++++
arch/s390/kvm/kvm-s390.h | 2 +
arch/s390/kvm/pv.c | 126 +++++++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 2 +
4 files changed, 154 insertions(+)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 141fb9d74ecd..f7952cef1309 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2284,6 +2284,30 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
set_bit(IRQ_PEND_EXT_SERVICE, &kvm->arch.float_int.masked_irqs);
break;
}
+ case KVM_PV_ASYNC_DISABLE_PREPARE:
+ r = -EINVAL;
+ if (!kvm_s390_pv_is_protected(kvm) || !lazy_destroy)
+ break;
+
+ r = kvm_s390_cpus_from_pv(kvm, &cmd->rc, &cmd->rrc);
+ /*
+ * If a CPU could not be destroyed, destroy VM will also fail.
+ * There is no point in trying to destroy it. Instead return
+ * the rc and rrc from the first CPU that failed destroying.
+ */
+ if (r)
+ break;
+ r = kvm_s390_pv_deinit_vm_async_prepare(kvm, &cmd->rc, &cmd->rrc);
+
+ /* no need to block service interrupts any more */
+ clear_bit(IRQ_PEND_EXT_SERVICE, &kvm->arch.float_int.masked_irqs);
+ break;
+ case KVM_PV_ASYNC_DISABLE:
+ r = -EINVAL;
+ if (!kvm->arch.pv.async_deinit)
+ break;
+ r = kvm_s390_pv_deinit_vm_async(kvm, &cmd->rc, &cmd->rrc);
+ break;
case KVM_PV_DISABLE: {
r = -EINVAL;
if (!kvm_s390_pv_is_protected(kvm))
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 9276d910631b..be53c7750248 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -234,6 +234,8 @@ static inline unsigned long kvm_s390_get_gfn_end(struct kvm_memslots *slots)
/* implemented in pv.c */
int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
int kvm_s390_pv_create_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
+int kvm_s390_pv_deinit_vm_async_prepare(struct kvm *kvm, u16 *rc, u16 *rrc);
+int kvm_s390_pv_deinit_vm_async(struct kvm *kvm, u16 *rc, u16 *rrc);
int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc);
int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc);
int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 6098af63f112..7b0b3b5e386b 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -262,6 +262,132 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
return cc ? -EIO : 0;
}
+/**
+ * kvm_s390_clear_2g - Clear the first 2GB of guest memory.
+ * @kvm the VM whose memory is to be cleared.
+ * Clear the first 2GB of guest memory, to avoid prefix issues after reboot.
+ */
+static void kvm_s390_clear_2g(struct kvm *kvm)
+{
+ struct kvm_memory_slot *slot;
+ unsigned long lim;
+ int srcu_idx;
+
+ srcu_idx = srcu_read_lock(&kvm->srcu);
+
+ slot = gfn_to_memslot(kvm, 0);
+ /* Clear all slots that are completely below 2GB */
+ while (slot && slot->base_gfn + slot->npages < SZ_2G / PAGE_SIZE) {
+ lim = slot->userspace_addr + slot->npages * PAGE_SIZE;
+ s390_uv_destroy_range(kvm->mm, slot->userspace_addr, lim);
+ slot = gfn_to_memslot(kvm, slot->base_gfn + slot->npages);
+ }
+ /* Last slot crosses the 2G boundary, clear only up to 2GB */
+ if (slot && slot->base_gfn < SZ_2G / PAGE_SIZE) {
+ lim = slot->userspace_addr + SZ_2G - slot->base_gfn * PAGE_SIZE;
+ s390_uv_destroy_range(kvm->mm, slot->userspace_addr, lim);
+ }
+
+ srcu_read_unlock(&kvm->srcu, srcu_idx);
+}
+
+/**
+ * kvm_s390_pv_deinit_vm_async_prepare - Prepare a protected VM for
+ * asynchronous teardown.
+ * @kvm the VM
+ * @rc return value for the RC field of the UVCB
+ * @rrc return value for the RRC field of the UVCB
+ *
+ * Prepare the protected VM for asynchronous teardown. The VM will be able
+ * to continue immediately as a non-secure VM, and the information needed to
+ * properly tear down the protected VM is set aside. If another protected VM
+ * was already set aside without starting a teardown, the function will
+ * fail.
+ *
+ * Context: kvm->lock needs to be held
+ *
+ * Return: 0 in case of success, -EINVAL if another protected VM was already set
+ * aside, -ENOMEM if the system ran out of memory.
+ */
+int kvm_s390_pv_deinit_vm_async_prepare(struct kvm *kvm, u16 *rc, u16 *rrc)
+{
+ struct deferred_priv *priv;
+
+ /*
+ * If an asynchronous deinitialization is already pending, refuse.
+ * A synchronous deinitialization has to be performed instead.
+ */
+ if (kvm->arch.pv.async_deinit)
+ return -EINVAL;
+ priv = kmalloc(sizeof(*priv), GFP_KERNEL | __GFP_ZERO);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->stor_var = kvm->arch.pv.stor_var;
+ priv->stor_base = kvm->arch.pv.stor_base;
+ priv->handle = kvm_s390_pv_get_handle(kvm);
+ priv->old_table = (unsigned long)kvm->arch.gmap->table;
+ WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
+ if (s390_replace_asce(kvm->arch.gmap)) {
+ kfree(priv);
+ return -ENOMEM;
+ }
+
+ kvm_s390_clear_2g(kvm);
+ kvm_s390_clear_pv_state(kvm);
+ kvm->arch.pv.async_deinit = priv;
+
+ *rc = 1;
+ *rrc = 42;
+ return 0;
+}
+
+/**
+ * kvm_s390_pv_deinit_vm_async - Perform an asynchronous teardown of a
+ * protected VM.
+ * @kvm the VM previously associated with the protected VM
+ * @rc return value for the RC field of the UVCB
+ * @rrc return value for the RRC field of the UVCB
+ *
+ * Tear down the protected VM that had previously been set aside using
+ * kvm_s390_pv_deinit_vm_async_prepare.
+ *
+ * Context: kvm->lock needs to be held
+ *
+ * Return: 0 in case of success, -EINVAL if no protected VM had been
+ * prepared for asynchronous teardowm, -EIO in case of other errors.
+ */
+int kvm_s390_pv_deinit_vm_async(struct kvm *kvm, u16 *rc, u16 *rrc)
+{
+ struct deferred_priv *p = kvm->arch.pv.async_deinit;
+ int ret = 0;
+
+ if (!p)
+ return -EINVAL;
+ kvm->arch.pv.async_deinit = NULL;
+ mutex_unlock(&kvm->lock);
+
+ /* When a fatal signal is received, stop immediately */
+ if (s390_uv_destroy_range_interruptible(kvm->mm, 0, TASK_SIZE_MAX))
+ goto done;
+ if (kvm_s390_pv_cleanup_deferred(kvm, p))
+ ret = -EIO;
+ else
+ atomic_dec(&kvm->mm->context.protected_count);
+ kfree(p);
+ p = NULL;
+done:
+ /* The caller expects the lock to be held */
+ mutex_lock(&kvm->lock);
+ /*
+ * p is not NULL if we aborted because of a fatal signal, in which
+ * case queue the leftover for later cleanup.
+ */
+ if (p)
+ list_add(&p->list, &kvm->arch.pv.need_cleanup);
+ return ret;
+}
+
static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
struct mm_struct *mm)
{
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b46bcdb0cab1..7f574c87a6ba 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1646,6 +1646,8 @@ enum pv_cmd_id {
KVM_PV_VERIFY,
KVM_PV_PREP_RESET,
KVM_PV_UNSHARE_ALL,
+ KVM_PV_ASYNC_DISABLE_PREPARE,
+ KVM_PV_ASYNC_DISABLE,
};
struct kvm_pv_cmd {
--
2.34.1
Refactor kvm_s390_pv_deinit_vm to improve readability and simplify the
improvements that are coming in subsequent patches.
No functional change intended.
[note: this can potentially be squashed into the next patch, I factored
it out to simplify the review process]
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/kvm/pv.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index d3b8fd9b5b3e..4e4728ec83a7 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -180,17 +180,17 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
- if (!cc)
- atomic_dec(&kvm->mm->context.protected_count);
- KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
- WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
- /* Intended memory leak on "impossible" error */
if (!cc) {
+ atomic_dec(&kvm->mm->context.protected_count);
kvm_s390_pv_dealloc_vm(kvm);
- return 0;
+ } else {
+ /* Intended memory leak on "impossible" error */
+ s390_replace_asce(kvm->arch.gmap);
}
- s390_replace_asce(kvm->arch.gmap);
- return -EIO;
+ KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
+ WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
+
+ return cc ? -EIO : 0;
}
static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
--
2.34.1
On Mon, 7 Feb 2022 15:52:37 +0100
Janosch Frank <[email protected]> wrote:
> On 2/4/22 16:53, Claudio Imbrenda wrote:
> > Add documentation for the new commands added to the KVM_S390_PV_COMMAND
> > ioctl.
> >
> > Signed-off-by: Claudio Imbrenda <[email protected]>
> > ---
> > Documentation/virt/kvm/api.rst | 21 ++++++++++++++++++---
> > 1 file changed, 18 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> > index a4267104db50..3b9068aceead 100644
> > --- a/Documentation/virt/kvm/api.rst
> > +++ b/Documentation/virt/kvm/api.rst
> > @@ -5010,11 +5010,13 @@ KVM_PV_ENABLE
> > ===== =============================
> >
> > KVM_PV_DISABLE
> > -
> > Deregister the VM from the Ultravisor and reclaim the memory that
> > had been donated to the Ultravisor, making it usable by the kernel
> > - again. All registered VCPUs are converted back to non-protected
> > - ones.
> > + again. All registered VCPUs are converted back to non-protected
> > + ones. If a previous VM had been prepared for asynchonous teardown
> > + with KVM_PV_ASYNC_DISABLE_PREPARE and not actually torn down with
> > + KVM_PV_ASYNC_DISABLE, it will be torn down in this call together with
> > + the current VM.
> >
> > KVM_PV_VM_SET_SEC_PARMS
> > Pass the image header from VM memory to the Ultravisor in
> > @@ -5027,6 +5029,19 @@ KVM_PV_VM_VERIFY
> > Verify the integrity of the unpacked image. Only if this succeeds,
> > KVM is allowed to start protected VCPUs.
> >
> > +KVM_PV_ASYNC_DISABLE_PREPARE
> > + Prepare the current protected VM for asynchronous teardown. The current
>
> I think the first sentence needs a few more examples of what we do so
> the second sentence makes more sense.
>
> ...by setting aside the pointers to the donated storage, replacing the
> top most page table, destroying the first 2GB of memory and zeroing the
> KVM PV structs.
I'm not sure we should give out implementation details, which might
change with newer kernel and/or hardware versions
>
>
> Or something which sounds a bit nicer.
>
> > + VM will then continue immediately as non-protected. If a protected VM had
> > + already been set aside without starting the teardown process, this call
> > + will fail. In this case the userspace process should issue a normal
> > + KVM_PV_DISABLE.
> > +
> > +KVM_PV_ASYNC_DISABLE
> > + Tear down the protected VM previously set aside for asynchronous teardown.
> > + This PV command should ideally be issued by userspace from a separate
> > + thread. If a fatal signal is received (or the process terminates
> > + naturally), the command will terminate immediately without completing.
> > +
> > 4.126 KVM_X86_SET_MSR_FILTER
> > ----------------------------
> >
> >
>
On Mon, 7 Feb 2022 09:56:39 +0100
Janosch Frank <[email protected]> wrote:
> On 2/4/22 16:53, Claudio Imbrenda wrote:
> > Each secure guest must have a unique ASCE (address space control
> > element); we must avoid that new guests use the same page for their
> > ASCE, to avoid errors.
> >
> > Since the ASCE mostly consists of the address of the topmost page table
> > (plus some flags), we must not return that memory to the pool unless
> > the ASCE is no longer in use.
> >
> > Only a successful Destroy Secure Configuration UVC will make the ASCE
> > reusable again.
> >
> > If the Destroy Configuration UVC fails, the ASCE cannot be reused for a
> > secure guest (either for the ASCE or for other memory areas). To avoid
> > a collision, it must not be used again. This is a permanent error and
> > the page becomes in practice unusable, so we set it aside and leak it.
> > On failure we already leak other memory that belongs to the ultravisor
> > (i.e. the variable and base storage for a guest) and not leaking the
> > topmost page table was an oversight.
> >
> > This error (and thus the leakage) should not happen unless the hardware
> > is broken or KVM has some unknown serious bug.
> >
> > Signed-off-by: Claudio Imbrenda <[email protected]>
> > Fixes: 29b40f105ec8d55 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
> > ---
> > arch/s390/include/asm/gmap.h | 2 ++
> > arch/s390/kvm/pv.c | 9 +++--
> > arch/s390/mm/gmap.c | 69 ++++++++++++++++++++++++++++++++++++
> > 3 files changed, 77 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> > index 40264f60b0da..746e18bf8984 100644
> > --- a/arch/s390/include/asm/gmap.h
> > +++ b/arch/s390/include/asm/gmap.h
> > @@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
> > unsigned long gaddr, unsigned long vmaddr);
> > int gmap_mark_unmergeable(void);
> > void s390_reset_acc(struct mm_struct *mm);
> > +void s390_remove_old_asce(struct gmap *gmap);
> > +int s390_replace_asce(struct gmap *gmap);
> > #endif /* _ASM_S390_GMAP_H */
> > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> > index 7f7c0d6af2ce..3c59ef763dde 100644
> > --- a/arch/s390/kvm/pv.c
> > +++ b/arch/s390/kvm/pv.c
> > @@ -166,10 +166,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> > atomic_set(&kvm->mm->context.is_protected, 0);
> > KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> > WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> > - /* Inteded memory leak on "impossible" error */
> > - if (!cc)
> > + /* Intended memory leak on "impossible" error */
> > + if (!cc) {
> > kvm_s390_pv_dealloc_vm(kvm);
> > - return cc ? -EIO : 0;
> > + return 0;
> > + }
> > + s390_replace_asce(kvm->arch.gmap);
> > + return -EIO;
> > }
> >
> > int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> > index dfee0ebb2fac..ce6cac4463f2 100644
> > --- a/arch/s390/mm/gmap.c
> > +++ b/arch/s390/mm/gmap.c
> > @@ -2714,3 +2714,72 @@ void s390_reset_acc(struct mm_struct *mm)
> > mmput(mm);
> > }
> > EXPORT_SYMBOL_GPL(s390_reset_acc);
> > +
> > +/**
> > + * s390_remove_old_asce - Remove the topmost level of page tables from the
> > + * list of page tables of the gmap.
> > + * @gmap the gmap whose table is to be removed
> > + *
> > + * This means that it will not be freed when the VM is torn down, and needs
> > + * to be handled separately by the caller, unless an intentional leak is
> > + * intended.
> > + */
> > +void s390_remove_old_asce(struct gmap *gmap)
> > +{
> > + struct page *old;
> > +
> > + old = virt_to_page(gmap->table);
> > + spin_lock(&gmap->guest_table_lock);
> > + list_del(&old->lru);
> > + /*
> > + * in case the ASCE needs to be "removed" multiple times, for example
> > + * if the VM is rebooted into secure mode several times
> > + * concurrently.
> > + */
> > + INIT_LIST_HEAD(&old->lru);
> > + spin_unlock(&gmap->guest_table_lock);
>
> The patch itself looks fine to me, but there's one oddity which made me
> look twice:
>
> You're not overwriting gmap->table here so you can use it in the
> function below. I guess that's intentional so it can still be used as a
> reference until we switch over to the new ASCE page?
yes. maybe I should rename the function or add more comments explaining
that the page is only removed from the list, so that it will not be freed at
teardown, but it's still in use by the VM (because we always need an
ASCE)
>
>
> > +}
> > +EXPORT_SYMBOL_GPL(s390_remove_old_asce);
> > +
> > +/**
> > + * s390_replace_asce - Try to replace the current ASCE of a gmap with
> > + * another equivalent one.
> > + * @gmap the gmap
> > + *
> > + * If the allocation of the new top level page table fails, the ASCE is not
> > + * replaced.
> > + * In any case, the old ASCE is always removed from the list. Therefore the
> > + * caller has to make sure to save a pointer to it beforehands, unless an > + * intentional leak is intended.
> > + */
> > +int s390_replace_asce(struct gmap *gmap)
> > +{
> > + unsigned long asce;
> > + struct page *page;
> > + void *table;
> > +
> > + s390_remove_old_asce(gmap);
> > +
> > + page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
> > + if (!page)
> > + return -ENOMEM;
> > + table = page_to_virt(page);
> > + memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
> > +
> > + /*
> > + * The caller has to deal with the old ASCE, but here we make sure
> > + * the new one is properly added to the list of page tables, so that
> > + * it will be freed when the VM is torn down.
> > + */
> > + spin_lock(&gmap->guest_table_lock);
> > + list_add(&page->lru, &gmap->crst_list);
> > + spin_unlock(&gmap->guest_table_lock);
> > +
> > + asce = (gmap->asce & ~PAGE_MASK) | __pa(table);
>
> Please add a comment:
> Set the new table origin while preserving ASCE control bits like table
> type and length.
will do
>
> > + WRITE_ONCE(gmap->asce, asce);
> > + WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
> > + WRITE_ONCE(gmap->table, table);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(s390_replace_asce);
> >
>
When ptep_get_and_clear_full is called for a mm teardown, we will now
attempt to destroy the secure pages. This will be faster than export.
In case it was not a teardown, or if for some reason the destroy page
UVC failed, we try with an export page, like before.
Signed-off-by: Claudio Imbrenda <[email protected]>
Acked-by: Janosch Frank <[email protected]>
---
arch/s390/include/asm/pgtable.h | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 23ca0d8e058a..72544a1b4a68 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1118,9 +1118,21 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
} else {
res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
}
- /* At this point the reference through the mapping is still present */
- if (mm_is_protected(mm) && pte_present(res))
- uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
+ /* Nothing to do */
+ if (!mm_is_protected(mm) || !pte_present(res))
+ return res;
+ /*
+ * At this point the reference through the mapping is still present.
+ * The notifier should have destroyed all protected vCPUs at this
+ * point, so the destroy should be successful.
+ */
+ if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
+ return res;
+ /*
+ * But if something went wrong and the pages could not be destroyed,
+ * the slower export is used as fallback instead.
+ */
+ uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
return res;
}
--
2.34.1
> > + asce = (gmap->asce & ~PAGE_MASK) | __pa(table);
>
> Please add a comment:
> Set the new table origin while preserving ASCE control bits like table type
> and length.
And while touching this anyway, please make use of _ASCE_ORIGIN
instead of PAGE_MASK.
On 2/4/22 16:53, Claudio Imbrenda wrote:
> Add documentation for the new commands added to the KVM_S390_PV_COMMAND
> ioctl.
>
> Signed-off-by: Claudio Imbrenda <[email protected]>
> ---
> Documentation/virt/kvm/api.rst | 21 ++++++++++++++++++---
> 1 file changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index a4267104db50..3b9068aceead 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5010,11 +5010,13 @@ KVM_PV_ENABLE
> ===== =============================
>
> KVM_PV_DISABLE
> -
> Deregister the VM from the Ultravisor and reclaim the memory that
> had been donated to the Ultravisor, making it usable by the kernel
> - again. All registered VCPUs are converted back to non-protected
> - ones.
> + again. All registered VCPUs are converted back to non-protected
> + ones. If a previous VM had been prepared for asynchonous teardown
> + with KVM_PV_ASYNC_DISABLE_PREPARE and not actually torn down with
> + KVM_PV_ASYNC_DISABLE, it will be torn down in this call together with
> + the current VM.
>
> KVM_PV_VM_SET_SEC_PARMS
> Pass the image header from VM memory to the Ultravisor in
> @@ -5027,6 +5029,19 @@ KVM_PV_VM_VERIFY
> Verify the integrity of the unpacked image. Only if this succeeds,
> KVM is allowed to start protected VCPUs.
>
> +KVM_PV_ASYNC_DISABLE_PREPARE
> + Prepare the current protected VM for asynchronous teardown. The current
I think the first sentence needs a few more examples of what we do so
the second sentence makes more sense.
...by setting aside the pointers to the donated storage, replacing the
top most page table, destroying the first 2GB of memory and zeroing the
KVM PV structs.
Or something which sounds a bit nicer.
> + VM will then continue immediately as non-protected. If a protected VM had
> + already been set aside without starting the teardown process, this call
> + will fail. In this case the userspace process should issue a normal
> + KVM_PV_DISABLE.
> +
> +KVM_PV_ASYNC_DISABLE
> + Tear down the protected VM previously set aside for asynchronous teardown.
> + This PV command should ideally be issued by userspace from a separate
> + thread. If a fatal signal is received (or the process terminates
> + naturally), the command will terminate immediately without completing.
> +
> 4.126 KVM_X86_SET_MSR_FILTER
> ----------------------------
>
>
On 2/4/22 16:53, Claudio Imbrenda wrote:
> Each secure guest must have a unique ASCE (address space control
> element); we must avoid that new guests use the same page for their
> ASCE, to avoid errors.
>
> Since the ASCE mostly consists of the address of the topmost page table
> (plus some flags), we must not return that memory to the pool unless
> the ASCE is no longer in use.
>
> Only a successful Destroy Secure Configuration UVC will make the ASCE
> reusable again.
>
> If the Destroy Configuration UVC fails, the ASCE cannot be reused for a
> secure guest (either for the ASCE or for other memory areas). To avoid
> a collision, it must not be used again. This is a permanent error and
> the page becomes in practice unusable, so we set it aside and leak it.
> On failure we already leak other memory that belongs to the ultravisor
> (i.e. the variable and base storage for a guest) and not leaking the
> topmost page table was an oversight.
>
> This error (and thus the leakage) should not happen unless the hardware
> is broken or KVM has some unknown serious bug.
>
> Signed-off-by: Claudio Imbrenda <[email protected]>
> Fixes: 29b40f105ec8d55 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
> ---
> arch/s390/include/asm/gmap.h | 2 ++
> arch/s390/kvm/pv.c | 9 +++--
> arch/s390/mm/gmap.c | 69 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 77 insertions(+), 3 deletions(-)
>
> diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> index 40264f60b0da..746e18bf8984 100644
> --- a/arch/s390/include/asm/gmap.h
> +++ b/arch/s390/include/asm/gmap.h
> @@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
> unsigned long gaddr, unsigned long vmaddr);
> int gmap_mark_unmergeable(void);
> void s390_reset_acc(struct mm_struct *mm);
> +void s390_remove_old_asce(struct gmap *gmap);
> +int s390_replace_asce(struct gmap *gmap);
> #endif /* _ASM_S390_GMAP_H */
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 7f7c0d6af2ce..3c59ef763dde 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -166,10 +166,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> atomic_set(&kvm->mm->context.is_protected, 0);
> KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> - /* Inteded memory leak on "impossible" error */
> - if (!cc)
> + /* Intended memory leak on "impossible" error */
> + if (!cc) {
> kvm_s390_pv_dealloc_vm(kvm);
> - return cc ? -EIO : 0;
> + return 0;
> + }
> + s390_replace_asce(kvm->arch.gmap);
> + return -EIO;
> }
>
> int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index dfee0ebb2fac..ce6cac4463f2 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2714,3 +2714,72 @@ void s390_reset_acc(struct mm_struct *mm)
> mmput(mm);
> }
> EXPORT_SYMBOL_GPL(s390_reset_acc);
> +
> +/**
> + * s390_remove_old_asce - Remove the topmost level of page tables from the
> + * list of page tables of the gmap.
> + * @gmap the gmap whose table is to be removed
> + *
> + * This means that it will not be freed when the VM is torn down, and needs
> + * to be handled separately by the caller, unless an intentional leak is
> + * intended.
> + */
> +void s390_remove_old_asce(struct gmap *gmap)
> +{
> + struct page *old;
> +
> + old = virt_to_page(gmap->table);
> + spin_lock(&gmap->guest_table_lock);
> + list_del(&old->lru);
> + /*
> + * in case the ASCE needs to be "removed" multiple times, for example
> + * if the VM is rebooted into secure mode several times
> + * concurrently.
> + */
> + INIT_LIST_HEAD(&old->lru);
> + spin_unlock(&gmap->guest_table_lock);
The patch itself looks fine to me, but there's one oddity which made me
look twice:
You're not overwriting gmap->table here so you can use it in the
function below. I guess that's intentional so it can still be used as a
reference until we switch over to the new ASCE page?
> +}
> +EXPORT_SYMBOL_GPL(s390_remove_old_asce);
> +
> +/**
> + * s390_replace_asce - Try to replace the current ASCE of a gmap with
> + * another equivalent one.
> + * @gmap the gmap
> + *
> + * If the allocation of the new top level page table fails, the ASCE is not
> + * replaced.
> + * In any case, the old ASCE is always removed from the list. Therefore the
> + * caller has to make sure to save a pointer to it beforehands, unless an > + * intentional leak is intended.
> + */
> +int s390_replace_asce(struct gmap *gmap)
> +{
> + unsigned long asce;
> + struct page *page;
> + void *table;
> +
> + s390_remove_old_asce(gmap);
> +
> + page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
> + if (!page)
> + return -ENOMEM;
> + table = page_to_virt(page);
> + memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
> +
> + /*
> + * The caller has to deal with the old ASCE, but here we make sure
> + * the new one is properly added to the list of page tables, so that
> + * it will be freed when the VM is torn down.
> + */
> + spin_lock(&gmap->guest_table_lock);
> + list_add(&page->lru, &gmap->crst_list);
> + spin_unlock(&gmap->guest_table_lock);
> +
> + asce = (gmap->asce & ~PAGE_MASK) | __pa(table);
Please add a comment:
Set the new table origin while preserving ASCE control bits like table
type and length.
> + WRITE_ONCE(gmap->asce, asce);
> + WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
> + WRITE_ONCE(gmap->table, table);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(s390_replace_asce);
>
Add an mmu_notifier for protected VMs. The callback function is
triggered when the mm is torn down, and will attempt to convert all
protected vCPUs to non-protected. This allows the mm teardown to use
the destroy page UVC instead of export.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/include/asm/kvm_host.h | 2 ++
arch/s390/kvm/pv.c | 20 ++++++++++++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index a22c9266ea05..1bccb8561ba9 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -19,6 +19,7 @@
#include <linux/kvm.h>
#include <linux/seqlock.h>
#include <linux/module.h>
+#include <linux/mmu_notifier.h>
#include <asm/debug.h>
#include <asm/cpu.h>
#include <asm/fpu/api.h>
@@ -921,6 +922,7 @@ struct kvm_s390_pv {
u64 guest_len;
unsigned long stor_base;
void *stor_var;
+ struct mmu_notifier mmu_notifier;
};
struct kvm_arch{
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index f1e812a45acb..d3b8fd9b5b3e 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -193,6 +193,21 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
return -EIO;
}
+static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
+ struct mm_struct *mm)
+{
+ struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
+ u16 dummy;
+
+ mutex_lock(&kvm->lock);
+ kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+ mutex_unlock(&kvm->lock);
+}
+
+static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {
+ .release = kvm_s390_pv_mmu_notifier_release,
+};
+
int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
{
struct uv_cb_cgc uvcb = {
@@ -234,6 +249,11 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
return -EIO;
}
kvm->arch.gmap->guest_handle = uvcb.guest_handle;
+ /* Add the notifier only once. No races because we hold kvm->lock */
+ if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) {
+ kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops;
+ mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
+ }
return 0;
}
--
2.34.1
On 2/4/22 16:53, Claudio Imbrenda wrote:
> The functions kvm_s390_cpus_from_pv needs to be called from pv.c, so
> make it global.
KVM: s390: pv: Add kvm_s390_cpus_from_pv to kvm-s390.h and provide
documentation
Future changes make it necessary to call this function from pv.c.
While we're add it let's properly document kvm_s390_cpus_from_pv() and
kvm_s390_cpus_to_pv().
Also could you swap patches 8 and 9 so this one is closer to patch #10?
Reviewed-by: Janosch Frank <[email protected]>
>
> Take the opportunity to add documentation.
>
> Signed-off-by: Claudio Imbrenda <[email protected]>
> ---
> arch/s390/kvm/kvm-s390.c | 26 +++++++++++++++++++++++++-
> arch/s390/kvm/kvm-s390.h | 1 +
> 2 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 1a788f45d691..0fc8d1aec396 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2175,7 +2175,20 @@ static int kvm_s390_set_cmma_bits(struct kvm *kvm,
> return r;
> }
>
> -static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
> +/**
> + * kvm_s390_cpus_from_pv - Convert all protected vCPUs in a protected VM to
> + * non protected.
> + * @kvm the VM whose protected vCPUs are to be converted
> + * @rcp return value for the RC field of the UVC (in case of error)
> + * @rrcp return value for the RRC field of the UVC (in case of error)
> + *
> + * Does not stop in case of error, tries to convert as many
> + * CPUs as possible. In case of error, the RC and RRC of the last error are
> + * returned.
> + *
> + * Return: 0 in case of success, otherwise -EIO
> + */
> +int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
> {
> struct kvm_vcpu *vcpu;
> u16 rc, rrc;
> @@ -2202,6 +2215,17 @@ static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
> return ret;
> }
>
> +/**
> + * kvm_s390_cpus_to_pv - Convert all non-protected vCPUs in a protected VM
> + * to protected.
> + * @kvm the VM whose protected vCPUs are to be converted
> + * @rcp return value for the RC field of the UVC (in case of error)
> + * @rrcp return value for the RRC field of the UVC (in case of error)
> + *
> + * Tries to undo the conversion in case of error.
> + *
> + * Return: 0 in case of success, otherwise -EIO
> + */
> static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
> {
> unsigned long i;
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 098831e815e6..9276d910631b 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -365,6 +365,7 @@ int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
> void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu);
> void kvm_s390_set_cpu_timer(struct kvm_vcpu *vcpu, __u64 cputm);
> __u64 kvm_s390_get_cpu_timer(struct kvm_vcpu *vcpu);
> +int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp);
>
> /* implemented in diag.c */
> int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);
>
Add KVM_CAP_S390_PROT_REBOOT_ASYNC to signal that the
KVM_PV_ASYNC_DISABLE and KVM_PV_ASYNC_DISABLE_PREPARE commands for the
KVM_S390_PV_COMMAND ioctl are available.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/kvm/kvm-s390.c | 3 +++
include/uapi/linux/kvm.h | 1 +
2 files changed, 4 insertions(+)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index f7952cef1309..1e696202a569 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -608,6 +608,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_BPB:
r = test_facility(82);
break;
+ case KVM_CAP_S390_PROT_REBOOT_ASYNC:
+ r = lazy_destroy && is_prot_virt_host();
+ break;
case KVM_CAP_S390_PROTECTED:
r = is_prot_virt_host();
break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 7f574c87a6ba..c41c108f6b14 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1134,6 +1134,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_VM_GPA_BITS 207
#define KVM_CAP_XSAVE2 208
#define KVM_CAP_SYS_ATTRIBUTES 209
+#define KVM_CAP_S390_PROT_REBOOT_ASYNC 215
#ifdef KVM_CAP_IRQ_ROUTING
--
2.34.1
On Mon, 7 Feb 2022 15:33:15 +0100
Heiko Carstens <[email protected]> wrote:
> > > + asce = (gmap->asce & ~PAGE_MASK) | __pa(table);
> >
> > Please add a comment:
> > Set the new table origin while preserving ASCE control bits like table type
> > and length.
>
> And while touching this anyway, please make use of _ASCE_ORIGIN
> instead of PAGE_MASK.
will fix
In upcoming patches it will be possible to start tearing down a
protected VM, and finish the teardown concurrently in a different
thread.
Protected VMs that are pending for tear down ("leftover") need to be
cleaned properly when the userspace process (e.g. qemu) terminates.
This patch makes sure that all "leftover" protected VMs are always
properly torn down.
Signed-off-by: Claudio Imbrenda <[email protected]>
---
arch/s390/include/asm/kvm_host.h | 2 +
arch/s390/kvm/kvm-s390.c | 1 +
arch/s390/kvm/pv.c | 69 ++++++++++++++++++++++++++++++++
3 files changed, 72 insertions(+)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 1bccb8561ba9..50e3516cbc03 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -922,6 +922,8 @@ struct kvm_s390_pv {
u64 guest_len;
unsigned long stor_base;
void *stor_var;
+ void *async_deinit;
+ struct list_head need_cleanup;
struct mmu_notifier mmu_notifier;
};
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 0fc8d1aec396..141fb9d74ecd 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2787,6 +2787,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
kvm_s390_vsie_init(kvm);
if (use_gisa)
kvm_s390_gisa_init(kvm);
+ INIT_LIST_HEAD(&kvm->arch.pv.need_cleanup);
KVM_EVENT(3, "vm 0x%pK created by pid %u", kvm, current->pid);
return 0;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 4e4728ec83a7..6098af63f112 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -16,6 +16,19 @@
#include <linux/sched/mm.h>
#include "kvm-s390.h"
+/**
+ * @struct deferred_priv
+ * Represents a "leftover" protected VM that does not correspond to any
+ * active KVM VM.
+ */
+struct deferred_priv {
+ struct list_head list;
+ unsigned long old_table;
+ u64 handle;
+ void *stor_var;
+ unsigned long stor_base;
+};
+
static void kvm_s390_clear_pv_state(struct kvm *kvm)
{
kvm->arch.pv.handle = 0;
@@ -163,6 +176,60 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
return -ENOMEM;
}
+/**
+ * kvm_s390_pv_cleanup_deferred - Clean up one leftover protected VM.
+ * @kvm the KVM that was associated with this leftover protected VM
+ * @deferred details about the leftover protected VM that needs a clean up
+ * Return: 0 in case of success, otherwise 1
+ */
+static int kvm_s390_pv_cleanup_deferred(struct kvm *kvm, struct deferred_priv *deferred)
+{
+ u16 rc, rrc;
+ int cc;
+
+ cc = uv_cmd_nodata(deferred->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
+ KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", rc, rrc);
+ WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
+ if (cc)
+ return cc;
+ /*
+ * Intentionally leak unusable memory. If the UVC fails, the memory
+ * used for the VM and its metadata is permanently unusable.
+ * This can only happen in case of a serious KVM or hardware bug; it
+ * is not expected to happen in normal operation.
+ */
+ free_pages(deferred->stor_base, get_order(uv_info.guest_base_stor_len));
+ free_pages(deferred->old_table, CRST_ALLOC_ORDER);
+ vfree(deferred->stor_var);
+ return 0;
+}
+
+/**
+ * kvm_s390_pv_cleanup_leftovers - Clean up all leftover protected VMs.
+ * @kvm the KVM whose leftover protected VMs are to be cleaned up
+ * Return: 0 in case of success, otherwise 1
+ */
+static int kvm_s390_pv_cleanup_leftovers(struct kvm *kvm)
+{
+ struct deferred_priv *deferred;
+ int cc = 0;
+
+ if (kvm->arch.pv.async_deinit)
+ list_add(kvm->arch.pv.async_deinit, &kvm->arch.pv.need_cleanup);
+
+ while (!list_empty(&kvm->arch.pv.need_cleanup)) {
+ deferred = list_first_entry(&kvm->arch.pv.need_cleanup, typeof(*deferred), list);
+ if (kvm_s390_pv_cleanup_deferred(kvm, deferred))
+ cc = 1;
+ else
+ atomic_dec(&kvm->mm->context.protected_count);
+ list_del(&deferred->list);
+ kfree(deferred);
+ }
+ kvm->arch.pv.async_deinit = NULL;
+ return cc;
+}
+
/* this should not fail, but if it does, we must not free the donated memory */
int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
{
@@ -190,6 +257,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
+ cc |= kvm_s390_pv_cleanup_leftovers(kvm);
+
return cc ? -EIO : 0;
}
--
2.34.1
On 2/4/22 16:53, Claudio Imbrenda wrote:
> Add KVM_CAP_S390_PROT_REBOOT_ASYNC to signal that the
> KVM_PV_ASYNC_DISABLE and KVM_PV_ASYNC_DISABLE_PREPARE commands for the
> KVM_S390_PV_COMMAND ioctl are available.
>
> Signed-off-by: Claudio Imbrenda <[email protected]>
> ---
> arch/s390/kvm/kvm-s390.c | 3 +++
> include/uapi/linux/kvm.h | 1 +
> 2 files changed, 4 insertions(+)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index f7952cef1309..1e696202a569 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -608,6 +608,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_S390_BPB:
> r = test_facility(82);
> break;
> + case KVM_CAP_S390_PROT_REBOOT_ASYNC:
> + r = lazy_destroy && is_prot_virt_host();
While reboot might be the best use-case for the async disable I don't
think we should name the capability this way.
KVM_CAP_S390_PROTECTED_ASYNC_DESTR ?
It's a bit long but the initial capability didn't abbreviate the
protected part so it is what it is.
> + break;
> case KVM_CAP_S390_PROTECTED:
> r = is_prot_virt_host();
> break;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 7f574c87a6ba..c41c108f6b14 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1134,6 +1134,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_VM_GPA_BITS 207
> #define KVM_CAP_XSAVE2 208
> #define KVM_CAP_SYS_ATTRIBUTES 209
> +#define KVM_CAP_S390_PROT_REBOOT_ASYNC 215
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
>
On 2/4/22 16:53, Claudio Imbrenda wrote:
> Refactor kvm_s390_pv_deinit_vm to improve readability and simplify the
> improvements that are coming in subsequent patches.
>
> No functional change intended.
>
> [note: this can potentially be squashed into the next patch, I factored
> it out to simplify the review process]
>
Reviewed-by: Janosch Frank <[email protected]>
> Signed-off-by: Claudio Imbrenda <[email protected]>
> ---
> arch/s390/kvm/pv.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index d3b8fd9b5b3e..4e4728ec83a7 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -180,17 +180,17 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
> UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
> WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
> - if (!cc)
> - atomic_dec(&kvm->mm->context.protected_count);
> - KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> - WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> - /* Intended memory leak on "impossible" error */
> if (!cc) {
> + atomic_dec(&kvm->mm->context.protected_count);
> kvm_s390_pv_dealloc_vm(kvm);
> - return 0;
> + } else {
> + /* Intended memory leak on "impossible" error */
> + s390_replace_asce(kvm->arch.gmap);
> }
> - s390_replace_asce(kvm->arch.gmap);
> - return -EIO;
> + KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> + WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> +
> + return cc ? -EIO : 0;
> }
>
> static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
>