KVM: x86: emulating descriptor load misses long-mode case

In 64-bit mode a #GP should be delivered to the guest "if the code segment descriptor pointed to by the selector in the 64-bit gate doesn't have the L-bit set and the D-bit clear." - Intel SDM "Interrupt 13â€”General Protection Exception (#GP)". This patch fixes the behavior of CS loading emulation code. Although the comment says that segment loading is not supported in long mode, this function is executed in long mode, so the fix is necassary. Signed-off-by: Nadav Amit <namit@cs.technion.ac.il> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
mariux64 · Sep 24, 2014 · 040c8dc · 040c8dc
1 parent 77c3913
commit 040c8dc
Showing 1 changed file with 9 additions and 0 deletions.
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
@@ -1504,6 +1504,15 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 			if (rpl > cpl || dpl != cpl)
 				goto exception;
 		}
+		/* in long-mode d/b must be clear if l is set */
+		if (seg_desc.d && seg_desc.l) {
+			u64 efer = 0;
+
+			ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
+			if (efer & EFER_LMA)
+				goto exception;
+		}
+
 		/* CS(RPL) <- CPL */
 		selector = (selector & 0xfffc) | cpl;
 		break;