[Intel-gfx] [PATCH 9/9] drm/i915/execlists: Prevent merging requests with conflicting flags

[Lionel Landwerlin]

On 10/10/2019 00:19, Chris Wilson wrote:
> We set out-of-bound parameters inside the i915_requests.flags field,
> such as disabling preemption or marking the end-of-context. We should
> not coalesce consecutive requests if they have differing instructions
> as we only inspect the last active request in a context. Thus if we
> allow a later request to be merged into the same execution context, it
> will mask any of the earlier flags.
>
> References: 2a98f4e65bba ("drm/i915: add infrastructure to hold off preemption on a request")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

Nice.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

> ---
>   drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 7ea58335f04c..d0687a94c8d9 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1233,6 +1233,9 @@ static bool can_merge_rq(const struct i915_request *prev,
>   	if (i915_request_completed(next))
>   		return true;
>   
> +	if (unlikely(prev->flags ^ next->flags) & I915_REQUEST_NOPREEMPT)
> +		return false;
> +
>   	if (!can_merge_ctx(prev->hw_context, next->hw_context))
>   		return false;
>