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 13—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>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 20d91873d8319e5fd0174124a7cf96bba082ef09..a46207a0583508ad662d179f2db1ede320a7645e 100644 (file)
--- 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;