KVM: VMX: update PFEC_MASK/PFEC_MATCH together with PF intercept (b502e6ec) · Commits · 戴 / test

The PFEC_MASK and PFEC_MATCH fields in the VMCS reverse the meaning of the #PF intercept bit in the exception bitmap when they do not match. This means that, if PFEC_MASK and/or PFEC_MATCH are set, the hypervisor can get a vmexit for #PF exceptions even when the corresponding bit is clear in the exception bitmap. This is unexpected and is promptly detected by a WARN_ON_ONCE. To fix it, reset PFEC_MASK and PFEC_MATCH when the #PF intercept is disabled (as is common with enable_ept && !allow_smaller_maxphyaddr). Reported-by:

Qian Cai <cai@redhat.com>> Reported-by:

Naresh Kamboju <naresh.kamboju@linaro.org> Tested-by:

Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

+12 −10

Original line number	Diff line number	Diff line
		@@ -794,6 +794,18 @@ void update_exception_bitmap(struct kvm_vcpu *vcpu)
		*/
		if (is_guest_mode(vcpu))
		eb \|= get_vmcs12(vcpu)->exception_bitmap;
		else {
		/*
		* If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched
		* between guest and host. In that case we only care about present
		* faults. For vmcs02, however, PFEC_MASK and PFEC_MATCH are set in
		* prepare_vmcs02_rare.
		*/
		bool selective_pf_trap = enable_ept && (eb & (1u << PF_VECTOR));
		int mask = selective_pf_trap ? PFERR_PRESENT_MASK : 0;
		vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, mask);
		vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, mask);
		}

		vmcs_write32(EXCEPTION_BITMAP, eb);
		}
		@@ -4355,16 +4367,6 @@ static void init_vmcs(struct vcpu_vmx *vmx)
		vmx->pt_desc.guest.output_mask = 0x7F;
		vmcs_write64(GUEST_IA32_RTIT_CTL, 0);
		}

		/*
		* If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched
		* between guest and host. In that case we only care about present
		* faults.
		*/
		if (enable_ept) {
		vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, PFERR_PRESENT_MASK);
		vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, PFERR_PRESENT_MASK);
		}
		}

		static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)

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