On Wed, Dec 04, 2019 at 03:51:00PM +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, 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
arch/x86/kvm/mmu/mmu.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 6f92b40d798c..8b8edfbdbaef 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -538,15 +538,11 @@ 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;
Removing this entirely will break CPUs that don't support leaf 0x80000008.
From a VMX perspective, I'm pretty sure all Intel hardware that supports
VMX is guaranteed to support 0x80000008, but I've no idea about SVM or any non-Intel CPU, and not supporting 0x80000008 in a virtual machine is technically legal/possible. We conditioned doing CPUID on TME because TME would be reported as supported iff 0x80000008 existed.
The extra bit of paranoia doesn't cost much, so play it safe? E.g.:
if (unlikely(boot_cpu_data.extended_cpuid_level < 0x80000008)) { WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_TME) || SME?); return boot_cpu_data.x86_phys_bits; }
return cpuid_eax(0x80000008) & 0xff;
- return cpuid_eax(0x80000008) & 0xff;
} -- 1.8.3.1