KVM: x86: Clear rflags.rf on emulated instructions

When an instruction is emulated RFLAGS.RF should be cleared. KVM previously did
not do so. This patch clears RFLAGS.RF after interception is done.  If a fault
occurs during the instruction, RFLAGS.RF will be set by a previous patch.  This
patch does not handle the case of traps/interrupts during rep-strings. Traps
are only expected to occur on debug watchpoints, and those are anyhow not
handled by the emulator.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

@@ -4640,6 +4640,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 			/* All REP prefixes have the same first termination condition */
 			if (address_mask(ctxt, reg_read(ctxt, VCPU_REGS_RCX)) == 0) {
 				ctxt->eip = ctxt->_eip;
+				ctxt->eflags &= ~EFLG_RF;
 				goto done;
 			}
 		}
@@ -4682,6 +4683,8 @@ special_insn:
 			goto done;
 	}
 
+	ctxt->eflags &= ~EFLG_RF;
+
 	if (ctxt->execute) {
 		if (ctxt->d & Fastop) {
 			void (*fop)(struct fastop *) = (void *)ctxt->execute;