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 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?

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

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