Re: [PATCH v1 1/4] KVM: MMU: check guest CR3 reserved bits based on its physical address width.

[Yu Zhang]

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;