On Wed, Dec 04, 2019 at 04:40:37PM +0100, Paolo Bonzini wrote:
> The comment in kvm_get_shadow_phys_bits refers to MKTME, but the same is actually
> true of SME and SEV. Just use CPUID[0x8000_0008].EAX[7:0] unconditionally if
> available, it is simplest and works even if memory is not encrypted.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++--------
> 1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 6f92b40d798c..1e4ee4f8de5f 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -538,16 +538,20 @@ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
> static u8 kvm_get_shadow_phys_bits(void)
> {
> /*
> - * boot_cpu_data.x86_phys_bits is reduced when MKTME is detected
> - * in CPU detection code, but MKTME treats those reduced bits as
> - * 'keyID' thus they are not reserved bits. Therefore for MKTME
> - * we should still return physical address bits reported by CPUID.
> + * boot_cpu_data.x86_phys_bits is reduced when MKTME or SME are detected
> + * in CPU detection code, but the processor treats those reduced bits as
> + * 'keyID' thus they are not reserved bits. Therefore KVM needs to look at
> + * the physical address bits reported by CPUID.
> */
> - if (!boot_cpu_has(X86_FEATURE_TME) ||
> - WARN_ON_ONCE(boot_cpu_data.extended_cpuid_level < 0x80000008))
> - return boot_cpu_data.x86_phys_bits;
> + if (likely(boot_cpu_data.extended_cpuid_level >= 0x80000008))
> + return cpuid_eax(0x80000008) & 0xff;
>
> - return cpuid_eax(0x80000008) & 0xff;
> + /*
> + * Quite weird to have VMX or SVM but not MAXPHYADDR; probably a VM with
> + * custom CPUID. Proceed with whatever the kernel found since these features
> + * aren't virtualizable (SME/SEV also require CPUIDs higher than 0x80000008).
No love for MKTME? :-D
Reviewed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> + */
> + return boot_cpu_data.x86_phys_bits;
> }
>
> static void kvm_mmu_reset_all_pte_masks(void)
> --
> 1.8.3.1
>
