Re: [PATCH 4/6] drm/i915/gt: Only invalidate TLBs exposed to user manipulation

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 15/06/2022 16:27, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Don't flush TLBs when the buffer is only used in the GGTT under full
> control of the kernel, as there's no risk of of concurrent access
> and stale access from prefetch.
> 
> We only need to invalidate the TLB if they are accessible by the user.
> 
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Same question as against the other patch - fix or optimisation?

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: stable@vger.kernel.org
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> ---
> 
> See [PATCH 0/6] at: https://lore.kernel.org/all/cover.1655306128.git.mchehab@kernel.org/
> 
>   drivers/gpu/drm/i915/i915_vma.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 0bffb70b3c5f..7989986161e8 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -537,7 +537,8 @@ int i915_vma_bind(struct i915_vma *vma,
>   				   bind_flags);
>   	}
>   
> -	set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
> +	if (bind_flags & I915_VMA_LOCAL_BIND)
> +		set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
>   
>   	atomic_or(bind_flags, &vma->flags);
>   	return 0;