Re: [PATCH v2] drm/i915/gvt: Adding ppgtt to GVT GEM context after pin.

[Zhenyu Wang <zhenyuw@linux.intel.com>]

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On 2019.07.04 16:00:55 +0800, Colin Xu wrote:
> 
> On 2019-07-04 15:43, Zhenyu Wang wrote:
> > On 2019.07.04 15:06:13 +0800, Colin Xu wrote:
> > > Windows guest can't run after force-TDR with host log:
> > > ...
> > > gvt: vgpu 1: workload shadow ppgtt isn't ready
> > > gvt: vgpu 1: fail to dispatch workload, skip
> > > ...
> > > 
> > > The error is raised by set_context_ppgtt_from_shadow(), when it checks
> > > and found the shadow_mm isn't marked as shadowed.
> > > 
> > > In work thread before each submission, a shadow_mm is set to shadowed in:
> > > shadow_ppgtt_mm()
> > > <-intel_vgpu_pin_mm()
> > > <-prepare_workload()
> > > <-dispatch_workload()
> > > <-workload_thread()
> > > However checking whether or not shadow_mm is shadowed is prior to it:
> > > set_context_ppgtt_from_shadow()
> > > <-dispatch_workload()
> > > <-workload_thread()
> > > 
> > > In normal case, create workload will check the existence of shadow_mm,
> > > if not it will create a new one and marked as shadowed. If already exist
> > > it will reuse the old one. Since shadow_mm is reused, checking of shadowed
> > > in set_context_ppgtt_from_shadow() actually always see the state set in
> > > creation, but not the state set in intel_vgpu_pin_mm().
> > > 
> > > When force-TDR, all engines are reset, since it's not dmlr level, all
> > > ppgtt_mm are invalidated but not destroyed. Invalidation will mark all
> > > reused shadow_mm as not shadowed but still keeps in ppgtt_mm_list_head.
> > > If workload submission phase those shadow_mm are reused with shadowed
> > > not set, then set_context_ppgtt_from_shadow() will report error.
> > > 
> > > Fixes: 4f15665ccbba (drm/i915: Add ppgtt to GVT GEM context)
> > > 
> > > v2:
> > > Move set_context_ppgtt_from_shadow() after prepare_workload(). (zhenyu)
> > > 
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Colin Xu <colin.xu@intel.com>
> > > ---
> > >   drivers/gpu/drm/i915/gvt/scheduler.c | 14 +++++++-------
> > >   1 file changed, 7 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
> > > index 196b4155a309..100040209188 100644
> > > --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> > > +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> > > @@ -685,13 +685,6 @@ static int dispatch_workload(struct intel_vgpu_workload *workload)
> > >   	mutex_lock(&vgpu->vgpu_lock);
> > >   	mutex_lock(&dev_priv->drm.struct_mutex);
> > > -	ret = set_context_ppgtt_from_shadow(workload,
> > > -					    s->shadow[ring_id]->gem_context);
> > > -	if (ret < 0) {
> > > -		gvt_vgpu_err("workload shadow ppgtt isn't ready\n");
> > > -		goto err_req;
> > > -	}
> > > -
> > >   	ret = intel_gvt_workload_req_alloc(workload);
> > >   	if (ret)
> > >   		goto err_req;
> > > @@ -707,6 +700,13 @@ static int dispatch_workload(struct intel_vgpu_workload *workload)
> > >   	}
> > >   	ret = prepare_workload(workload);
> > > +	if (ret)
> > > +		goto out;
> > > +
> > > +	ret = set_context_ppgtt_from_shadow(workload,
> > > +					    s->shadow[ring_id]->gem_context);
> > > +	if (ret)
> > > +		gvt_vgpu_err("workload shadow ppgtt isn't ready\n");
> > As workload's shadow_mm should always be for ppgtt, so we don't need return
> > for set_context_ppgtt_from_shadow, can just be void. Then how about do that
> > in prepare_workload after we settle down shadow pdp?
> > 
> If so, is checking mm->type and shadowed flag stil necessary? since intel_vgpu_pin_mm()
> in prepare_workload will guaranee that, if intel_vgpu_pin_mm() fails, shadow pdp won't
> get updated and no need to pin. Am I right?
>

yep, I think so.

> > >   out:
> > >   	if (ret) {
> > >   		/* We might still need to add request with
> > > -- 
> > > 2.22.0
> > > 
> -- 
> Best Regards,
> Colin Xu
> 

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