From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 18 Aug 2014 11:15:51 +0000 (+0200)
Subject: KVM: x86: do not check CS.DPL against RPL during task switch
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9a4cfb27f7233610c5ddc82329c26d39683fad72;p=linux.git

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

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@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 ef117b8423345..03954f7900f52 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;