[PATCH 15/45] KVM: SVM: Fix cross vendor migration issue in segment segment descriptor

[Avi Kivity]

From: Andre Przywara <andre.przywara@xxxxxxx>

On AMD CPUs sometimes the DB bit in the stack segment
descriptor is left as 1, although the whole segment has
been made unusable. Clear it here to pass an Intel VMX
entry check when cross vendor migrating.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
 arch/x86/kvm/svm.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 6350378..e3ea982 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -803,6 +803,15 @@ static void svm_get_segment(struct kvm_vcpu *vcpu,
 		if (!var->unusable)
 			var->type |= 0x1;
 		break;
+	case VCPU_SREG_SS:
+		/* On AMD CPUs sometimes the DB bit in the segment
+		 * descriptor is left as 1, although the whole segment has
+		 * been made unusable. Clear it here to pass an Intel VMX
+		 * entry check when cross vendor migrating.
+		 */
+		if (var->unusable)
+			var->db = 0;
+		break;
 	}
 }
 
-- 
1.6.0.6

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