[PATCH 3.12 099/122] KVM: x86: emulating descriptor load misses long-mode case

From: Jiri Slaby
Date: Tue Feb 17 2015 - 06:43:36 EST

From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


commit 040c8dc8a5afa7364bb8bb5b1b76c30007d6be14 upstream.

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 13ÃââGeneral 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@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
arch/x86/kvm/emulate.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 987fdb379df6..d28104924255 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1533,6 +1533,15 @@ 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;

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