From: Jan Dakinevich jan.dakinevich@virtuozzo.com
commit 8530a79c5a9f4e29e6ffb35ec1a79d81f4968ec8 upstream.
inject_emulated_exception() returns true if and only if nested page fault happens. However, page fault can come from guest page tables walk, either nested or not nested. In both cases we should stop an attempt to read under RIP and give guest to step over its own page fault handler.
This is also visible when an emulated instruction causes a #GP fault and the VMware backdoor is enabled. To handle the VMware backdoor, KVM intercepts #GP faults; with only the next patch applied, x86_emulate_instruction() injects a #GP but returns EMULATE_FAIL instead of EMULATE_DONE. EMULATE_FAIL causes handle_exception_nmi() (or gp_interception() for SVM) to re-inject the original #GP because it thinks emulation failed due to a non-VMware opcode. This patch prevents the issue as x86_emulate_instruction() will return EMULATE_DONE after injecting the #GP.
Fixes: 6ea6e84309ca ("KVM: x86: inject exceptions produced by x86_decode_insn") Cc: stable@vger.kernel.org Cc: Denis Lunev den@virtuozzo.com Cc: Roman Kagan rkagan@virtuozzo.com Cc: Denis Plotnikov dplotnikov@virtuozzo.com Signed-off-by: Jan Dakinevich jan.dakinevich@virtuozzo.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/x86.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5486,8 +5486,10 @@ int x86_emulate_instruction(struct kvm_v if (reexecute_instruction(vcpu, cr2, write_fault_to_spt, emulation_type)) return EMULATE_DONE; - if (ctxt->have_exception && inject_emulated_exception(vcpu)) + if (ctxt->have_exception) { + inject_emulated_exception(vcpu); return EMULATE_DONE; + } if (emulation_type & EMULTYPE_SKIP) return EMULATE_FAIL; return handle_emulation_failure(vcpu);