[PATCH] KVM: x86: do not check CS.DPL against RPL during task switch

From: Paolo Bonzini
Date: Wed Aug 20 2014 - 07:20:15 EST


This reverts the check added by commit 5045b468037d (KVM: x86: check CS.DPL
against RPL during task switch, 2014-05-15). Although the CS.DPL=CS.RPL
check is mentioned in table 7-1 of the SDM as causing a #TSS exception,
it is not mentioned in table 6-6 that lists "invalid TSS conditions"
which cause #TSS exceptions. In fact it causes some tests to fail, which
pass on bare-metal.

Keep the rest of the commit, since we will find new uses for it in 3.18.

Reported-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index ef117b842334..03954f7900f5 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1491,9 +1491,6 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
goto exception;
break;
case VCPU_SREG_CS:
- if (in_task_switch && rpl != dpl)
- goto exception;
-
if (!(seg_desc.type & 8))
goto exception;

--
1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/