Re: [PATCH] drm/i915: Add an optional selection from i915 of CONFIG_MMU_NOTIFIER

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

On 07/21/2015 01:16 PM, Chris Wilson wrote:
> userptr requires mmu-notifier for full unprivileged support. Most
> systems have mmu-notifier support already enabled as a requirement for
> virtualisation support, but we should make the option for i915 to take
> advantage of mmu-notifiers explicit (and enable by default so that
> regular userspace can take advantage of passing client memory to the
> GPU.)
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/Kconfig | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index eb87e2538861..1e33195e4a12 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -62,3 +62,14 @@ config DRM_I915_PRELIMINARY_HW_SUPPORT
>   	  option changes the default for that module option.
>
>   	  If in doubt, say "N".
> +
> +config DRM_I915_USERPTR
> +	bool "Always enable userptr support"
> +	depends on DRM_I915
> +	select MMU_NOTIFIER
> +	default y
> +	help
> +	  This option selects CONFIG_MMU_NOTIFIER if it isn't already
> +	  selected to enabled full userptr support.

s/enabled/enable/

I think it needs more text under help to explain what are you giving up 
if N, or to justify Y in other words. For distro kernels it is 
irrelevant but advanced users will want to know.

But since overall I think it is justified, in principle:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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