linux-kernel - Re: [PATCH] drm/i915/ttm: fix large buffer population trucation

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Date:   Mon, 13 Dec 2021 13:02:44 +0000
From:   Matthew Auld <matthew.auld@...el.com>
To:     Robert Beckett <bob.beckett@...labora.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>, Oak Zeng <oak.zeng@...el.com>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915/ttm: fix large buffer population trucation

On 10/12/2021 19:50, Robert Beckett wrote:
> ttm->num_pages is uint32_t which was causing very large buffers to
> only populate a truncated size.
> 
> This fixes gem_create@...ate-clear igt test on large memory systems.
> 
> Fixes: 7ae034590cea ("drm/i915/ttm: add tt shmem backend")
> Signed-off-by: Robert Beckett <bob.beckett@...labora.com>

Nice catch,
Reviewed-by: Matthew Auld <matthew.auld@...el.com>

> ---
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 218a9b3037c7..923cc7ad8d70 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -166,7 +166,7 @@ static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
>   	struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
>   	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
>   	const unsigned int max_segment = i915_sg_segment_size();
> -	const size_t size = ttm->num_pages << PAGE_SHIFT;
> +	const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
>   	struct file *filp = i915_tt->filp;
>   	struct sgt_iter sgt_iter;
>   	struct sg_table *st;
>