From 6ce347af1499deff5890a52aedacd451330af706 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 22 Apr 2020 19:25:38 -0700 Subject: [PATCH] KVM: nVMX: Preserve exception priority irrespective of exiting behavior Short circuit vmx_check_nested_events() if an exception is pending and needs to be injected into L2, priority between coincident events is not dependent on exiting behavior. This fixes a bug where a single-step #DB that is not intercepted by L1 is incorrectly dropped due to servicing a VMX Preemption Timer VM-Exit. Injected exceptions also need to be blocked if nested VM-Enter is pending or an exception was already injected, otherwise injecting the exception could overwrite an existing event injection from L1. Technically, this scenario should be impossible, i.e. KVM shouldn't inject its own exception during nested VM-Enter. This will be addressed in a future patch. Note, event priority between SMI, NMI and INTR is incorrect for L2, e.g. SMI should take priority over VM-Exit on NMI/INTR, and NMI that is injected into L2 should take priority over VM-Exit INTR. This will also be addressed in a future patch. Fixes: b6b8a1451fc4 ("KVM: nVMX: Rework interception of IRQs and NMIs") Reported-by: Jim Mattson Cc: Oliver Upton Cc: Peter Shier Signed-off-by: Sean Christopherson Message-Id: <20200423022550.15113-2-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/nested.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index b644bbf85460d..de678be3c92d6 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3716,11 +3716,11 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu) /* * Process any exceptions that are not debug traps before MTF. */ - if (vcpu->arch.exception.pending && - !vmx_pending_dbg_trap(vcpu) && - nested_vmx_check_exception(vcpu, &exit_qual)) { + if (vcpu->arch.exception.pending && !vmx_pending_dbg_trap(vcpu)) { if (block_nested_events) return -EBUSY; + if (!nested_vmx_check_exception(vcpu, &exit_qual)) + goto no_vmexit; nested_vmx_inject_exception_vmexit(vcpu, exit_qual); return 0; } @@ -3733,10 +3733,11 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu) return 0; } - if (vcpu->arch.exception.pending && - nested_vmx_check_exception(vcpu, &exit_qual)) { + if (vcpu->arch.exception.pending) { if (block_nested_events) return -EBUSY; + if (!nested_vmx_check_exception(vcpu, &exit_qual)) + goto no_vmexit; nested_vmx_inject_exception_vmexit(vcpu, exit_qual); return 0; } @@ -3771,6 +3772,7 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu) return 0; } +no_vmexit: vmx_complete_nested_posted_interrupt(vcpu); return 0; } -- 2.30.2