On Mon, Jan 30, 2012 at 12:24:11PM +0200, Avi Kivity wrote:
> > +
> > ctxt->ops->set_segment(ctxt, selector, &desc, base3, seg);
> > }
> >
> > @@ -2273,6 +2281,24 @@ static int load_state_from_tss32(struct
> > x86_emulate_ctxt *ctxt,
> > return emulate_gp(ctxt, 0);
> > ctxt->_eip = tss->eip;
> > ctxt->eflags = tss->eflags | 2;
> > +
> > + /*
> > + * If we're switching between Protected Mode and VM86, we need to make
> > + * sure to update the mode before loading the segment descriptors so
> > + * that the selectors are interpreted correctly.
> > + *
> > + * Need to get it to the vcpu struct immediately because it influences
> > + * the CPL which is checked at least when loading the segment
> > + * descriptors and when pushing an error code to the new kernel stack.
> > + */
> > + if (ctxt->eflags & X86_EFLAGS_VM)
> > + ctxt->mode = X86EMUL_MODE_VM86;
> > + else
> > + ctxt->mode = X86EMUL_MODE_PROT32;
> > +
>
> Shouldn't this be done after the set_segment_selector() block? My
> interpretation of the SDM is that if a fault happens while loading
> descriptors the fault happens with old segment cache, that is, it needs
> to be interpreted according to the old mode.
>
No, spec says:
Any errors associated with this loading and qualification occur in the
context of the new task.
--
Gleb.
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