TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
(0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
zeros on CPUID #VEs. In practice, this means that the kernel can only
boot with a plain topology. Any complications will cause problems.
The ENUM_TOPOLOGY feature allows the VMM to provide topology
information to the guest in a safe manner. Enabling the feature
eliminates topology-related #VEs: the TDX module virtualizes
accesses to the CPUID leafs and the MSR.
Enable ENUM_TOPOLOGY if it is available.
Signed-off-by: Kirill A. Shutemov <[email protected]>
---
arch/x86/coco/tdx/tdx.c | 20 ++++++++++++++++++++
arch/x86/include/asm/shared/tdx.h | 3 +++
2 files changed, 23 insertions(+)
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index d9ea82f8772d..291e45db8d54 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -280,6 +280,26 @@ static void tdx_setup(u64 *cc_mask)
else
tdx_panic(msg);
}
+
+ /*
+ * TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
+ * (0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
+ * zeros on CPUID #VEs. In practice, this means that the kernel can only
+ * boot with a plain topology. Any complications will cause problems.
+ *
+ * The ENUM_TOPOLOGY feature allows the VMM to provide topology
+ * information to the guest in a safe manner. Enabling the feature
+ * eliminates topology-related #VEs: the TDX module virtualizes
+ * accesses to the CPUID leafs and the MSR.
+ *
+ * Enable ENUM_TOPOLOGY if it is available.
+ */
+ if ((features & TDX_FEATURES0_ENUM_TOPOLOGY) &&
+ tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED)) {
+ tdg_vm_wr(TDCS_TD_CTLS,
+ TD_CTLS_ENUM_TOPOLOGY,
+ TD_CTLS_ENUM_TOPOLOGY);
+ }
}
/*
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 29a61c72e4dd..2964c506b241 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -27,15 +27,18 @@
#define TDCS_CONFIG_FLAGS 0x1110000300000016
#define TDCS_TD_CTLS 0x1110000300000017
#define TDCS_NOTIFY_ENABLES 0x9100000000000010
+#define TDCS_TOPOLOGY_ENUM_CONFIGURED 0x9100000000000019
/* TDCS_TDX_FEATURES0 bits */
#define TDX_FEATURES0_PENDING_EPT_VIOLATION_V2 BIT_ULL(16)
+#define TDX_FEATURES0_ENUM_TOPOLOGY BIT_ULL(20)
/* TDCS_CONFIG_FLAGS bits */
#define TDCS_CONFIG_FLEXIBLE_PENDING_VE BIT_ULL(1)
/* TDCS_TD_CTLS bits */
#define TD_CTLS_PENDING_VE_DISABLE BIT_ULL(0)
+#define TD_CTLS_ENUM_TOPOLOGY BIT_ULL(1)
/* TDX hypercall Leaf IDs */
#define TDVMCALL_MAP_GPA 0x10001
--
2.43.0
On 3/9/24 1:02 PM, Kirill A. Shutemov wrote:
> TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
> (0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
> zeros on CPUID #VEs. In practice, this means that the kernel can only
> boot with a plain topology. Any complications will cause problems.
Is this issue only for TDX 1.0? What about TDX > 1.0?
>
> The ENUM_TOPOLOGY feature allows the VMM to provide topology
> information to the guest in a safe manner. Enabling the feature
> eliminates topology-related #VEs: the TDX module virtualizes
> accesses to the CPUID leafs and the MSR.
>
> Enable ENUM_TOPOLOGY if it is available.
I cant find the ENUM_TOPOLOGY in ABI spec (https://cdrdv2.intel.com/v1/dl/getContent/795381).
Can you point me to the correct document?
>
> Signed-off-by: Kirill A. Shutemov <[email protected]>
> ---
> arch/x86/coco/tdx/tdx.c | 20 ++++++++++++++++++++
> arch/x86/include/asm/shared/tdx.h | 3 +++
> 2 files changed, 23 insertions(+)
>
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index d9ea82f8772d..291e45db8d54 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -280,6 +280,26 @@ static void tdx_setup(u64 *cc_mask)
> else
> tdx_panic(msg);
> }
> +
> + /*
> + * TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
> + * (0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
> + * zeros on CPUID #VEs. In practice, this means that the kernel can only
> + * boot with a plain topology. Any complications will cause problems.
> + *
> + * The ENUM_TOPOLOGY feature allows the VMM to provide topology
> + * information to the guest in a safe manner. Enabling the feature
> + * eliminates topology-related #VEs: the TDX module virtualizes
> + * accesses to the CPUID leafs and the MSR.
> + *
> + * Enable ENUM_TOPOLOGY if it is available.
> + */
Why are we overriding it in guest? Why can't this by done by TDX Module
or QEMU during initialization?
> + if ((features & TDX_FEATURES0_ENUM_TOPOLOGY) &&
> + tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED)) {
> + tdg_vm_wr(TDCS_TD_CTLS,
> + TD_CTLS_ENUM_TOPOLOGY,
> + TD_CTLS_ENUM_TOPOLOGY);
> + }
> }
>
> /*
> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index 29a61c72e4dd..2964c506b241 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -27,15 +27,18 @@
> #define TDCS_CONFIG_FLAGS 0x1110000300000016
> #define TDCS_TD_CTLS 0x1110000300000017
> #define TDCS_NOTIFY_ENABLES 0x9100000000000010
> +#define TDCS_TOPOLOGY_ENUM_CONFIGURED 0x9100000000000019
>
> /* TDCS_TDX_FEATURES0 bits */
> #define TDX_FEATURES0_PENDING_EPT_VIOLATION_V2 BIT_ULL(16)
> +#define TDX_FEATURES0_ENUM_TOPOLOGY BIT_ULL(20)
>
> /* TDCS_CONFIG_FLAGS bits */
> #define TDCS_CONFIG_FLEXIBLE_PENDING_VE BIT_ULL(1)
>
> /* TDCS_TD_CTLS bits */
> #define TD_CTLS_PENDING_VE_DISABLE BIT_ULL(0)
> +#define TD_CTLS_ENUM_TOPOLOGY BIT_ULL(1)
>
> /* TDX hypercall Leaf IDs */
> #define TDVMCALL_MAP_GPA 0x10001
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
On Sat, Mar 09, 2024 at 07:56:11PM -0800, Kuppuswamy Sathyanarayanan wrote:
>
> On 3/9/24 1:02 PM, Kirill A. Shutemov wrote:
> > TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
> > (0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
> > zeros on CPUID #VEs. In practice, this means that the kernel can only
> > boot with a plain topology. Any complications will cause problems.
>
> Is this issue only for TDX 1.0? What about TDX > 1.0?
TDX 1.0 defines the baseline for TDX. Any change in behaviour will be
gated by explicit opt-in. In this case, it is ENUM_TOPOLOGY.
> > The ENUM_TOPOLOGY feature allows the VMM to provide topology
> > information to the guest in a safe manner. Enabling the feature
> > eliminates topology-related #VEs: the TDX module virtualizes
> > accesses to the CPUID leafs and the MSR.
> >
> > Enable ENUM_TOPOLOGY if it is available.
>
> I cant find the ENUM_TOPOLOGY in ABI spec (https://cdrdv2.intel.com/v1/dl/getContent/795381).
>
> Can you point me to the correct document?
I guess JSON dump is out of sync with the PDF doc. See this:
https://cdrdv2.intel.com/v1/dl/getContent/733579
--
Kiryl Shutsemau / Kirill A. Shutemov