Signed-off-by: Andrew Cooper
---
CC: Jan Beulich
---
xen/arch/x86/hvm/hvm.c | 24
1 file changed, 24 insertions(+)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index ceb89c7..3c90ecd 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2037,6 +2037,30 @@ int hvm_set_efer(uint64_t value)
return X86EMUL_EXCEPTION;
}
+if ( (value & EFER_LME) && !(v->arch.hvm_vcpu.guest_efer & EFER_LME) )
+{
+struct segment_register cs;
+
+hvm_get_segment_register(v, x86_seg_cs, &cs);
+
+/*
+ * %cs may be loaded with both .D and .L set in legacy mode, and both
+ * are captured in the VMCS/VMCB.
+ *
+ * If a guest does this and then tries to transition into long mode,
+ * the vmentry from setting LME fails due to invalid guest state,
+ * because %cr0.PG is still clear.
+ *
+ * When LME becomes set, clobber %cs.L to keep the guest firmly in
+ * compatibility mode until it reloads %cs itself.
+ */
+if ( cs.attr.fields.l )
+{
+cs.attr.fields.l = 0;
+hvm_set_segment_register(v, x86_seg_cs, &cs);
+}
+}
+
if ( nestedhvm_enabled(v->domain) && cpu_has_svm &&
((value & EFER_SVME) == 0 ) &&
((value ^ v->arch.hvm_vcpu.guest_efer) & EFER_SVME) )
--
2.1.4
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