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SubjectRe: [PATCH v1 1/4] KVM: MMU: check guest CR3 reserved bits based on its physical address width.
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On 8/14/2017 3:36 PM, Paolo Bonzini wrote:
> On 12/08/2017 15:35, Yu Zhang wrote:
>> + ctxt->ops->get_cpuid(ctxt, &eax, NULL, NULL, NULL);
>> + maxphyaddr = eax * 0xff;
> This is "&", not "*". You can also use rsvd_bits here.

Oops. Sorry for the typo. :-)

>> + rsvd = (~((1UL << maxphyaddr) - 1)) &
>> + ~CR3_PCID_INVD;
>> + }
>>
>> if (new_val & rsvd)
>> return emulate_gp(ctxt, 0);
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index e40a779..d9100c4 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -813,10 +813,10 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>> return 0;
>> }
>>
>> - if (is_long_mode(vcpu)) {
>> - if (cr3 & CR3_L_MODE_RESERVED_BITS)
>> - return 1;
>> - } else if (is_pae(vcpu) && is_paging(vcpu) &&
>> + if (is_long_mode(vcpu) &&
>> + (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 63)))
>> + return 1;
> 62 is a little better, since 63 is the PCID invalidate bit.

Got it. Both kvm_set_cr3() and check_cr_write() should use
rsvd_bits(maxphyaddr, 62) .

Thanks
Yu

> Paolo
>
>> + else if (is_pae(vcpu) && is_paging(vcpu) &&
>> !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
>> return 1;
>>
>

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