Re: [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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