Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | Re: [PATCH v2 1/4] KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit | Date | Thu, 7 Jan 2021 18:51:41 +0100 |
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On 07/01/21 18:00, Sean Christopherson wrote: > Ugh, I assume this is due to one of the "premature" nested_ops->check_events() > calls that are necessitated by the event mess? I'm guessing kvm_vcpu_running() > is the culprit? > > If my assumption is correct, this bug affects nVMX as well.
Yes, though it may be latent. For SVM it was until we started allocating svm->nested on demand.
> Rather than clear the request blindly on any nested VM-Exit, what > about something like the following?
I think your patch is overkill, KVM_REQ_GET_NESTED_STATE_PAGES is only set from KVM_SET_NESTED_STATE so it cannot happen while the VM runs.
Something like this is small enough and works well.
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index a622e63739b4..cb4c6ee10029 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -595,6 +596,8 @@ int nested_svm_vmexit(struct vcpu_svm *svm) svm->nested.vmcb12_gpa = 0; WARN_ON_ONCE(svm->nested.nested_run_pending);
+ kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, &svm->vcpu); + /* in case we halted in L2 */ svm->vcpu.arch.mp_state = KVM_MP_STATE_RUNNABLE;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index e2f26564a12d..0fbb46990dfc 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4442,6 +4442,8 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason, /* trying to cancel vmlaunch/vmresume is a bug */ WARN_ON_ONCE(vmx->nested.nested_run_pending);
+ kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu); + /* Service the TLB flush request for L2 before switching to L1. */ if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu)) kvm_vcpu_flush_tlb_current(vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3f7c1fc7a3ce..b7e784b5489c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8789,7 +8789,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (kvm_request_pending(vcpu)) { if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) { - if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) { + if (WARN_ON_ONCE(!is_guest_mode(&svm->vcpu))) + ; + else if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) { r = 0; goto out; }
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