KVM: x86: Do not update EFLAGS on faulting emulation

If the emulation ends in fault, eflags should not be updated.  However, several
instruction emulations (actually all the fastops) currently update eflags, if
the fault was detected afterwards (e.g., #PF during writeback).

Signed-off-by: Nadav Amit <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 641358865a0c98068c6c2a6f446e02fdcafd444d..da1591eeb4773e58ba476fd6c4c5e0c1a613e4db 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5360,7 +5360,9 @@ restart:
                kvm_rip_write(vcpu, ctxt->eip);
                if (r == EMULATE_DONE)
                        kvm_vcpu_check_singlestep(vcpu, rflags, &r);
-               __kvm_set_rflags(vcpu, ctxt->eflags);
+               if (!ctxt->have_exception ||
+                   exception_type(ctxt->exception.vector) == EXCPT_TRAP)
+                       __kvm_set_rflags(vcpu, ctxt->eflags);
 
                /*
                 * For STI, interrupts are shadowed; so KVM_REQ_EVENT will