On Wed, Apr 28, 2010 at 11:59:54AM +0300, Avi Kivity wrote:
> On 04/27/2010 03:15 PM, Gleb Natapov wrote:
> >Use callbacks from x86_emulate_ops to access segments instead of calling
> >into kvm directly.
> >
> >
> >
> >-static unsigned long seg_base(struct x86_emulate_ctxt *ctxt, int seg)
> >+static unsigned long seg_base(struct x86_emulate_ctxt *ctxt,
> >+ struct x86_emulate_ops *ops, int seg)
> > {
> >- if (ctxt->mode == X86EMUL_MODE_PROT64&& seg< VCPU_SREG_FS)
> >- return 0;
> >+ unsigned long base;
> >
> >- return kvm_x86_ops->get_segment_base(ctxt->vcpu, seg);
>
> get_segment_base() is only one vmread on intel, but you replace it
> with reading the entire segment.
>
Didn't what to have separate x86_emulate_ops callback for reading
segment base. If this is serious performance concern it can be added
> >+ if (ctxt->mode == X86EMUL_MODE_PROT64) {
> >+ u64 val;
> >+ switch (seg) {
> >+ case VCPU_SREG_FS:
> >+ ops->get_msr(ctxt->vcpu, MSR_FS_BASE,&val);
> >+ break;
> >+ case VCPU_SREG_GS:
> >+ ops->get_msr(ctxt->vcpu, MSR_GS_BASE,&val);
> >+ break;
> >+ default:
> >+ val = 0;
> >+ break;
> >+ }
>
> Why this ugliness? get_cached_descriptor() should do this.
>
get_cached_descriptor() returns struct desc_struct which is 32 bit only.
There is not 64bit segment descriptors.
> >
> > static unsigned long seg_override_base(struct x86_emulate_ctxt *ctxt,
> >+ struct x86_emulate_ops *ops,
> > struct decode_cache *c)
> > {
> > if (!c->has_seg_override)
> > return 0;
> >
> >- return seg_base(ctxt, c->seg_override);
> >+ return seg_base(ctxt, ops, c->seg_override);
> > }
>
> Sticking ops into ctxt would reduce the size of these patches.
>
But it will introduce intermediate huge patch. But I agree that this
should be done eventually. Planned to do it somewhere at the end. Near
the patch that change x86_emulate_ops callbacks to get ctxt instead of
vcpu as a parameter.
--
Gleb.
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