From: Avi Kivity <avi@redhat.com>
Date: Thu, 7 Jun 2012 14:03:42 +0000 (+0300)
Subject: KVM: x86 emulator: allow loading null SS in long mode
X-Git-Tag: v3.6-rc1~124^2~39
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=79d5b4c3cd809c770d4bf9812635647016c56011;p=~emulex%2Finfiniband.git

KVM: x86 emulator: allow loading null SS in long mode

Null SS is valid in long mode; allow loading it.

Signed-off-by: Avi Kivity <avi@redhat.com>
---

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index db95a55d593..fe4340f6213 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1324,8 +1324,14 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 		goto load;
 	}
 
-	/* NULL selector is not valid for TR, CS and SS */
-	if ((seg == VCPU_SREG_CS || seg == VCPU_SREG_SS || seg == VCPU_SREG_TR)
+	rpl = selector & 3;
+	cpl = ctxt->ops->cpl(ctxt);
+
+	/* NULL selector is not valid for TR, CS and SS (except for long mode) */
+	if ((seg == VCPU_SREG_CS
+	     || (seg == VCPU_SREG_SS
+		 && (ctxt->mode != X86EMUL_MODE_PROT64 || rpl != cpl))
+	     || seg == VCPU_SREG_TR)
 	    && null_selector)
 		goto exception;
 
@@ -1352,9 +1358,7 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 		goto exception;
 	}
 
-	rpl = selector & 3;
 	dpl = seg_desc.dpl;
-	cpl = ctxt->ops->cpl(ctxt);
 
 	switch (seg) {
 	case VCPU_SREG_SS: