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KVM: x86: use CPUID to locate host page table reserved bits

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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@vger.kernel.org
Reported-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2019-12-04 15:50:27 +01:00
parent c79f46a282
commit 7adacf5eb2
1 changed files with 12 additions and 8 deletions
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20
arch/x86/kvm/mmu/mmu.c
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@ -538,16 +538,20 @@ EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);
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).
*/
return boot_cpu_data.x86_phys_bits;
}
static void kvm_mmu_reset_all_pte_masks(void)