linux-kernel - [PATCH] KVM: x86: emulator injects #DB when RFLAGS.RF is set

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Date:	Thu, 17 Jul 2014 01:19:31 +0300
From:	Nadav Amit <namit@...technion.ac.il>
To:	pbonzini@...hat.com
Cc:	gleb@...nel.org, tglx@...utronix.de, mingo@...hat.com,
	x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Nadav Amit <namit@...technion.ac.il>
Subject: [PATCH] KVM: x86: emulator injects #DB when RFLAGS.RF is set

If the RFLAGS.RF is set, then no #DB should occur on instruction breakpoints.
However, the KVM emulator injects #DB regardless to RFLAGS.RF. This patch fixes
this behavior. KVM, however, still appears not to update RFLAGS.RF correctly,
regardless of this patch.

Signed-off-by: Nadav Amit <namit@...technion.ac.il>
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fae064f..e341a81 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5168,7 +5168,8 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
 		}
 	}
 
-	if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK)) {
+	if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK) &&
+	    !(kvm_get_rflags(vcpu) & X86_EFLAGS_RF)) {
 		dr6 = kvm_vcpu_check_hw_bp(eip, 0,
 					   vcpu->arch.dr7,
 					   vcpu->arch.db);
-- 
1.9.1

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