Commit 577bdc49 authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: Avoid instruction emulation when event delivery is pending 



When an event (such as an interrupt) is injected, and the stack is
shadowed (and therefore write protected), the guest will exit.  The
current code will see that the stack is shadowed and emulate a few
instructions, each time postponing the injection.  Eventually the
injection may succeed, but at that time the guest may be unwilling
to accept the interrupt (for example, the TPR may have changed).

This occurs every once in a while during a Windows 2008 boot.

Fix by unshadowing the fault address if the fault was due to an event
injection.

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 34198bf8

arch/x86/kvm/mmu.c

+1 −0
Original line number Diff line number Diff line
@@ -1814,6 +1814,7 @@ int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva) 
	spin_unlock(&vcpu->kvm->mmu_lock);

	return r;

}

EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page_virt);



void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)

{

arch/x86/kvm/svm.c

+6 −1
Original line number Diff line number Diff line
@@ -1008,10 +1008,13 @@ static int pf_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run) 
	struct kvm *kvm = svm->vcpu.kvm;

	u64 fault_address;

	u32 error_code;

	bool event_injection = false;



	if (!irqchip_in_kernel(kvm) &&

		is_external_interrupt(exit_int_info))

	    is_external_interrupt(exit_int_info)) {

		event_injection = true;

		push_irq(&svm->vcpu, exit_int_info & SVM_EVTINJ_VEC_MASK);

	}



	fault_address  = svm->vmcb->control.exit_info_2;

	error_code = svm->vmcb->control.exit_info_1;
@@ -1025,6 +1028,8 @@ static int pf_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run) 
			    (u32)fault_address, (u32)(fault_address >> 32),

			    handler);



	if (event_injection)

		kvm_mmu_unprotect_page_virt(&svm->vcpu, fault_address);

	return kvm_mmu_page_fault(&svm->vcpu, fault_address, error_code);

}

arch/x86/kvm/vmx.c

+2 −0
Original line number Diff line number Diff line
@@ -2298,6 +2298,8 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
		cr2 = vmcs_readl(EXIT_QUALIFICATION);

		KVMTRACE_3D(PAGE_FAULT, vcpu, error_code, (u32)cr2,

			    (u32)((u64)cr2 >> 32), handler);

		if (vect_info & VECTORING_INFO_VALID_MASK)

			kvm_mmu_unprotect_page_virt(vcpu, cr2);

		return kvm_mmu_page_fault(vcpu, cr2, error_code);

	}

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