linux-kernel - [PATCH 2/3] KVM: x86: Emulator support for #UD on CPL>0

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Message-Id: <1403101176-23664-3-git-send-email-namit@cs.technion.ac.il>
Date:	Wed, 18 Jun 2014 17:19:35 +0300
From:	Nadav Amit <namit@...technion.ac.il>
To:	pbonzini@...hat.com
Cc:	gleb@...nel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, joro@...tes.org,
	Nadav Amit <namit@...technion.ac.il>
Subject: [PATCH 2/3] KVM: x86: Emulator support for #UD on CPL>0

Certain instructions (e.g., mwait and monitor) cause a #UD exception when they
are executed in privilaged mode. This is in contrast to the regular privilaged
instructions which cause #GP. In order not to mess with SVM interception of
mwait and monitor which assumes privilage level assertions take place before
interception, a flag has been added.

Signed-off-by: Nadav Amit <namit@...technion.ac.il>
---
 arch/x86/kvm/emulate.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index f90194d..ef7a5a0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -163,6 +163,7 @@
 #define SrcWrite    ((u64)1 << 46)  /* Write back src operand */
 #define NoMod	    ((u64)1 << 47)  /* Mod field is ignored */
 #define NoBigReal   ((u64)1 << 48)  /* No big real mode */
+#define UDOnPriv    ((u64)1 << 49)  /* #UD instead of #GP on CPL > 0 */
 
 #define DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
 
@@ -4560,7 +4561,10 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 
 	/* Privileged instruction can be executed only in CPL=0 */
 	if ((ctxt->d & Priv) && ops->cpl(ctxt)) {
-		rc = emulate_gp(ctxt, 0);
+		if (ctxt->d & UDOnPriv)
+			rc = emulate_ud(ctxt);
+		else
+			rc = emulate_gp(ctxt, 0);
 		goto done;
 	}
 
-- 
1.9.1

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