From: Sean Christopherson seanjc@google.com
[ Upstream commit cd9e6da8048c5b40315ee2d929b6230ce1252c3c ]
Unwind the RIP advancement done by svm_queue_exception() when injecting an INT3 ultimately "fails" due to the CPU encountering a VM-Exit while vectoring the injected event, even if the exception reported by the CPU isn't the same event that was injected. If vectoring INT3 encounters an exception, e.g. #NP, and vectoring the #NP encounters an intercepted exception, e.g. #PF when KVM is using shadow paging, then the #NP will be reported as the event that was in-progress.
Note, this is still imperfect, as it will get a false positive if the INT3 is cleanly injected, no VM-Exit occurs before the IRET from the INT3 handler in the guest, the instruction following the INT3 generates an exception (directly or indirectly), _and_ vectoring that exception encounters an exception that is intercepted by KVM. The false positives could theoretically be solved by further analyzing the vectoring event, e.g. by comparing the error code against the expected error code were an exception to occur when vectoring the original injected exception, but SVM without NRIPS is a complete disaster, trying to make it 100% correct is a waste of time.
Reviewed-by: Maxim Levitsky mlevitsk@redhat.com Fixes: 66b7138f9136 ("KVM: SVM: Emulate nRIP feature when reinjecting INT3") Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Maciej S. Szmigiero maciej.szmigiero@oracle.com Message-Id: 450133cf0a026cb9825a2ff55d02cb136a1cb111.1651440202.git.maciej.szmigiero@oracle.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/svm/svm.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 2851d1e58cb8..e4c736d74fcb 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3613,6 +3613,18 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu) vector = exitintinfo & SVM_EXITINTINFO_VEC_MASK; type = exitintinfo & SVM_EXITINTINFO_TYPE_MASK;
+ /* + * If NextRIP isn't enabled, KVM must manually advance RIP prior to + * injecting the soft exception/interrupt. That advancement needs to + * be unwound if vectoring didn't complete. Note, the _new_ event may + * not be the injected event, e.g. if KVM injected an INTn, the INTn + * hit a #NP in the guest, and the #NP encountered a #PF, the #NP will + * be the reported vectored event, but RIP still needs to be unwound. + */ + if (int3_injected && type == SVM_EXITINTINFO_TYPE_EXEPT && + kvm_is_linear_rip(vcpu, svm->int3_rip)) + kvm_rip_write(vcpu, kvm_rip_read(vcpu) - int3_injected); + switch (type) { case SVM_EXITINTINFO_TYPE_NMI: vcpu->arch.nmi_injected = true; @@ -3626,16 +3638,11 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu)
/* * In case of software exceptions, do not reinject the vector, - * but re-execute the instruction instead. Rewind RIP first - * if we emulated INT3 before. + * but re-execute the instruction instead. */ - if (kvm_exception_is_soft(vector)) { - if (vector == BP_VECTOR && int3_injected && - kvm_is_linear_rip(vcpu, svm->int3_rip)) - kvm_rip_write(vcpu, - kvm_rip_read(vcpu) - int3_injected); + if (kvm_exception_is_soft(vector)) break; - } + if (exitintinfo & SVM_EXITINTINFO_VALID_ERR) { u32 err = svm->vmcb->control.exit_int_info_err; kvm_requeue_exception_e(vcpu, vector, err);