On Aug 18, 2014, at 12:09 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > Il 17/08/2014 21:32, Nadav Amit ha scritto: >> This reverts commit 5045b468037dfe1c848827ce10e99d87f5669160. 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. As it causes some tests, which pass on bare-metal, >> to fail - it should be reverted. > > Right. However, I think reverting the patch is too big a hammer. We > still need in_task_switch to raise TS_VECTOR instead of GP_VECTOR, so I > propose instead something like: > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 56657b0bb3bb..cd230b035514 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -1468,7 +1468,7 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, > return ret; > > err_code = selector & 0xfffc; > - err_vec = GP_VECTOR; > + err_vec = in_task_switch ? TS_VECTOR : GP_VECTOR; > > /* can't load system descriptor into segment selector */ > if (seg <= VCPU_SREG_GS && !seg_desc.s) > @@ -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; > > > either in a single patch or as two separate patch. I'll test this against > your test case and repost (not before Tuesday). > I missed the TS_VECTOR thing. Yes, in that case, full revert makes no sense. I’m in no hurry with this patch, and I posted it during your vacation only because it is a recent bug. Anyhow, you may want to look at another patch I sent, "KVM: x86: Avoid emulating instructions on #UD mistakenly”, ASAP. It fixes a bug that was introduced into 3.17-RC1 and is visible in userspace. Nadav
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