From 9a7de6ecc3ed80efb95fe1d97b6440922e55dbda Mon Sep 17 00:00:00 2001 From: Krish Sadhukhan Date: Tue, 23 Mar 2021 13:50:03 -0400 Subject: KVM: nSVM: If VMRUN is single-stepped, queue the #DB intercept in nested_svm_vmexit() According to APM, the #DB intercept for a single-stepped VMRUN must happen after the completion of that instruction, when the guest does #VMEXIT to the host. However, in the current implementation of KVM, the #DB intercept for a single-stepped VMRUN happens after the completion of the instruction that follows the VMRUN instruction. When the #DB intercept handler is invoked, it shows the RIP of the instruction that follows VMRUN, instead of of VMRUN itself. This is an incorrect RIP as far as single-stepping VMRUN is concerned. This patch fixes the problem by checking, in nested_svm_vmexit(), for the condition that the VMRUN instruction is being single-stepped and if so, queues the pending #DB intercept so that the #DB is accounted for before we execute L1's next instruction. Suggested-by: Paolo Bonzini Signed-off-by: Krish Sadhukhan Message-Id: <20210323175006.73249-2-krish.sadhukhan@oracle.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/nested.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'arch/x86/kvm/svm/nested.c') diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 9bed4847ad55..b974bd9c53c3 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -764,6 +764,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm) nested_svm_copy_common_state(svm->nested.vmcb02.ptr, svm->vmcb01.ptr); svm_switch_vmcb(svm, &svm->vmcb01); + WARN_ON_ONCE(svm->vmcb->control.exit_code != SVM_EXIT_VMRUN); /* * On vmexit the GIF is set to false and @@ -817,6 +818,15 @@ int nested_svm_vmexit(struct vcpu_svm *svm) kvm_clear_exception_queue(vcpu); kvm_clear_interrupt_queue(vcpu); + /* + * If we are here following the completion of a VMRUN that + * is being single-stepped, queue the pending #DB intercept + * right now so that it an be accounted for before we execute + * L1's next instruction. + */ + if (unlikely(svm->vmcb->save.rflags & X86_EFLAGS_TF)) + kvm_queue_exception(&(svm->vcpu), DB_VECTOR); + return 0; } -- cgit v1.2.3