KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit

It is possible to exit the nested guest mode, entered by
svm_set_nested_state prior to first vm entry to it (e.g due to pending event)
if the nested run was not pending during the migration.

In this case we must not switch to the nested msr permission bitmap.
Also add a warning to catch similar cases in the future.

Fixes: a7d5c7ce41ac1 ("KVM: nSVM: delay MSR permission processing to first nested VM run")

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210107093854.882483-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index a622e63..cb4c6ee 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -199,6 +199,7 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
 static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
+
        if (!nested_svm_vmrun_msrpm(svm)) {
                vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
                vcpu->run->internal.suberror =
@@ -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 e2f2656..0fbb469 100644 (file)
--- 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 e28ab76..f6e7b25 100644 (file)
--- 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(vcpu)))
+                               ;
+                       else if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) {
                                r = 0;
                                goto out;
                        }