[Intel-gfx] [PATCH] drm/i915/gt: Onion unwind for scratch page allocation failure

[Tang, CQ]

Reviewed-by: CQ Tang <cq.tang at intel.com>

--CQ

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of
> Chris Wilson
> Sent: Monday, October 19, 2020 1:35 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Auld, Matthew <matthew.auld at intel.com>; Chris Wilson <chris at chris-
> wilson.co.uk>
> Subject: [Intel-gfx] [PATCH] drm/i915/gt: Onion unwind for scratch page
> allocation failure
> 
> In switching to using objects for our ppGTT scratch pages, care was not taken
> to avoid trying to unref NULL objects on failure. And for gen6 ppGTT, it
> appears we forgot entirely to unwind after a partial allocation failure.
> 
> Fixes: 89351925a477 ("drm/i915/gt: Switch to object allocations for page
> directories")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gt/gen6_ppgtt.c | 18 ++++++++++++------
> drivers/gpu/drm/i915/gt/gen8_ppgtt.c |  3 ++-
>  2 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
> b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
> index c0d17f87b00f..680bd9442eb0 100644
> --- a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
> @@ -239,18 +239,24 @@ static int gen6_ppgtt_init_scratch(struct
> gen6_ppgtt *ppgtt)
>  			       I915_CACHE_NONE, PTE_READ_ONLY);
> 
>  	vm->scratch[1] = vm->alloc_pt_dma(vm, I915_GTT_PAGE_SIZE_4K);
> -	if (IS_ERR(vm->scratch[1]))
> -		return PTR_ERR(vm->scratch[1]);
> +	if (IS_ERR(vm->scratch[1])) {
> +		ret = PTR_ERR(vm->scratch[1]);
> +		goto err_scratch0;
> +	}
> 
>  	ret = pin_pt_dma(vm, vm->scratch[1]);
> -	if (ret) {
> -		i915_gem_object_put(vm->scratch[1]);
> -		return ret;
> -	}
> +	if (ret)
> +		goto err_scratch1;
> 
>  	fill32_px(vm->scratch[1], vm->scratch[0]->encode);
> 
>  	return 0;
> +
> +err_scratch1:
> +	i915_gem_object_put(vm->scratch[1]);
> +err_scratch0:
> +	i915_gem_object_put(vm->scratch[0]);
> +	return ret;
>  }
> 
>  static void gen6_ppgtt_free_pd(struct gen6_ppgtt *ppgtt) diff --git
> a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> index b236aa046f91..a37c968ef8f7 100644
> --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> @@ -607,7 +607,8 @@ static int gen8_init_scratch(struct i915_address_space
> *vm)
>  	return 0;
> 
>  free_scratch:
> -	free_scratch(vm);
> +	while (i--)
> +		i915_gem_object_put(vm->scratch[i]);
>  	return -ENOMEM;
>  }
> 
> --
> 2.20.1
> 
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