[PATCH] KVM: pass through CPUID 0x80000005

[PATCH] KVM: pass through CPUID 0x80000005

[Takahiro Itazuri]

Pass CPUID 0x80000005 (L1 cache and TLB info).

CPUID 0x80000006 (L2 cache and TLB and L3 cache info) has been returned
since commit 43d05de2bee7 ("KVM: pass through CPUID(0x80000006)").
Enumerating both 0x80000005 and 0x80000006 with KVM_GET_SUPPORTED_CPUID
would be better than reporting either, and 0x80000005 could be helpful
for VMM to pass it to KVM_SET_CPUID{,2} for the same reason with
0x80000006..

Signed-off-by: Takahiro Itazuri <itazur@amazon.com>
---

Discussion was made a bit on
https://lore.kernel.org/all/20230712170258.75355-1-itazur@amazon.com/.
If there is any reason that leaf 0x80000005 should not be enumerated or
dropping leaf 0x80000006 is preferred, please feel free to share your
thoughts.

---
 arch/x86/kvm/cpuid.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 0c9660a07b23..54a5b256c484 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1152,6 +1152,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		cpuid_entry_override(entry, CPUID_8000_0001_EDX);
 		cpuid_entry_override(entry, CPUID_8000_0001_ECX);
 		break;
+	case 0x80000005:
+		/*  Pass host L1 cache and TLB info. */
+		break;
 	case 0x80000006:
 		/* Drop reserved bits, pass host L2 cache and TLB info. */
 		entry->edx &= ~GENMASK(17, 16);
-- 
2.38.0

Re: [PATCH] KVM: pass through CPUID 0x80000005

[Sean Christopherson]

On Wed, 12 Jul 2023 19:31:36 +0100, Takahiro Itazuri wrote:
> Pass CPUID 0x80000005 (L1 cache and TLB info).
> 
> CPUID 0x80000006 (L2 cache and TLB and L3 cache info) has been returned
> since commit 43d05de2bee7 ("KVM: pass through CPUID(0x80000006)").
> Enumerating both 0x80000005 and 0x80000006 with KVM_GET_SUPPORTED_CPUID
> would be better than reporting either, and 0x80000005 could be helpful
> for VMM to pass it to KVM_SET_CPUID{,2} for the same reason with
> 0x80000006..
> 
> [...]

Applied to kvm-x86 misc, thanks!

[1/1] KVM: pass through CPUID 0x80000005
      https://github.com/kvm-x86/linux/commit/af8e2ccfa6f1

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes