KVM: SVM: set accessed bit for VMCB segment selectors

In the segment descriptor _cache_ the accessed bit is always set
(although it can be cleared in the descriptor itself). Since Intel
checks for this condition on a VMENTRY, set this bit in the AMD path
to enable cross vendor migration.

Cc: stable@kernel.org
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Acked-By: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 29 insertions, 12 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 22e88a4a51c7..1821c2078199 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -796,20 +796,37 @@ static void svm_get_segment(struct kvm_vcpu *vcpu,
         var->db = (s->attrib >> SVM_SELECTOR_DB_SHIFT) & 1;
         var->g = (s->attrib >> SVM_SELECTOR_G_SHIFT) & 1;
 
-        /*
-         * SVM always stores 0 for the 'G' bit in the CS selector in
-         * the VMCB on a VMEXIT. This hurts cross-vendor migration:
-         * Intel's VMENTRY has a check on the 'G' bit.
-         */
-        if (seg == VCPU_SREG_CS)
+        switch (seg) {
+        case VCPU_SREG_CS:
+                /*
+                 * SVM always stores 0 for the 'G' bit in the CS selector in
+                 * the VMCB on a VMEXIT. This hurts cross-vendor migration:
+                 * Intel's VMENTRY has a check on the 'G' bit.
+                 */
                 var->g = s->limit > 0xfffff;
-
-        /*
-         * Work around a bug where the busy flag in the tr selector
-         * isn't exposed
-         */
-        if (seg == VCPU_SREG_TR)
+                break;
+        case VCPU_SREG_TR:
+                /*
+                 * Work around a bug where the busy flag in the tr selector
+                 * isn't exposed
+                 */
                 var->type |= 0x2;
+                break;
+        case VCPU_SREG_DS:
+        case VCPU_SREG_ES:
+        case VCPU_SREG_FS:
+        case VCPU_SREG_GS:
+                /*
+                 * The accessed bit must always be set in the segment
+                 * descriptor cache, although it can be cleared in the
+                 * descriptor, the cached bit always remains at 1. Since
+                 * Intel has a check on this, set it here to support
+                 * cross-vendor migration.
+                 */
+                if (!var->unusable)
+                        var->type |= 0x1;
+                break;
+        }
 
         var->unusable = !var->present;
 }