[PATCH] drm/i915/gvt: Do not check shadowed when adding ppgtt to GVT GEM context

[Zhenyu Wang]

On 2019.07.04 10:55:15 +0800, Zhenyu Wang wrote:
> On 2019.07.04 08:09:29 +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.
> > 
> > No need to check shadowed state in set_context_ppgtt_from_shadow().
> 
> Thanks for tracing this! I think this is a side effect from 1e18d5e6731d674fee0bb4b66f5ea61e504452a3,
> which I moved this setting out of scan function.
> 
> One potential issue with this is shadow_pdps at this time might not have valid value yet,
> how about we move shadow ctx ppgtt setting after we really prepared mm for workload and
> before i915 submission? As this setting now is mostly to please i915, we have already set
> context's ppgtt by ourself.
> 
> > 
> > Fixes: 4f15665ccbba (drm/i915: Add ppgtt to GVT GEM context)
> > 
> > Signed-off-by: Colin Xu <colin.xu at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gvt/scheduler.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
> > index 196b4155a309..a5db57926962 100644
> > --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> > +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> > @@ -371,7 +371,7 @@ static int set_context_ppgtt_from_shadow(struct intel_vgpu_workload *workload,
> >  	struct i915_ppgtt *ppgtt = i915_vm_to_ppgtt(ctx->vm);
> >  	int i = 0;
> >  
> > -	if (mm->type != INTEL_GVT_MM_PPGTT || !mm->ppgtt_mm.shadowed)
> > +	if (mm->type != INTEL_GVT_MM_PPGTT)
> >  		return -EINVAL;
> >  
> >  	if (mm->ppgtt_mm.root_entry_type == GTT_TYPE_PPGTT_ROOT_L4_ENTRY) {
> > -- 

As 5.2 will be close to release, I think this fix might not be able to catch up,
pls make sure to cc stable kernel.

thanks

-- 
Open Source Technology Center, Intel ltd.

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