[PATCH v2 2/2] drm/i915/gvt: Support PPGTT table load command

[Zhenyu Wang]

On 2020.04.27 03:21:49 -0400, Yan Zhao wrote:
> > > 
> > > I think the step is just to restore guest context and run through
> > > loaded shadow mm, we only need to recover last guest pdp after
> > > workload run.
> > >
> > sorry. sent too fast.
> > I mean why not just update workload->shadow_mm and
> > workload->shadow_mm->ppgtt_mm.guest_pdps, when lri pdp is found?
> >
> 1. if lri pdp1 (not the same as shadow_mm) and lri pdp2 (the same as
> shadow_mm) are executed successively, we should not update the guest
> pdp.

Actually we should, to replace with shadow ppgtt ptr also for same as
shadow_mm case, otherwise wrong pdps would be loaded to HW. Next version
will fix that.

> 2. if there's a save inhibit bit set in the workload, we cannot
> update the guest context.

yep, looks currently we don't care about save inhibit but just update
guest context. We might do this later.

> 3. there may be other cases to cause last entry in lri_shadow_mm no
> aligning with the final one in workload.
> so I think the safest way to update guest context is to find the
> guest_pdps according to pdps in shadow context.

Hmm, I think it's safe now to mark last ppgtt LRI cmd as last context
state because I can't think of other ways might affect that. And to
find guest pdps, we have to walk through all shadow mm which seems not
worth to me.

Thanks

> 
> > > > > > > 
> > > > > > > and what's the reason for us to use a lri_shadow_mm list?
> > > > > > 
> > > > > > As in theory there could be multiple ppgtt loads in one ring
> > > > > > submission, and previous code always assumes one e.g put older scanned
> > > > > > shadow mm if found another one, which was not right to me. So here
> > > > > > just uses a link to track all possible loads.
> > > > > > 
> > > > > > > 
> > > > > > > 

-- 
Open Source Technology Center, Intel ltd.

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