linux-kernel - [PATCH 6/7] KVM: x86: Clear rflags.rf on emulated instructions

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Date:	Mon, 21 Jul 2014 14:37:29 +0300
From:	Nadav Amit <namit@...technion.ac.il>
To:	pbonzini@...hat.com
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, gleb@...nel.org, linux-kernel@...r.kernel.org,
	Nadav Amit <namit@...technion.ac.il>
Subject: [PATCH 6/7] 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@...technion.ac.il>
---
 arch/x86/kvm/emulate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index cf117bf..189b8bd8 100644
--- a/arch/x86/kvm/emulate.c
+++ b/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;
-- 
1.9.1

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