Re: [Intel-gfx] [PATCH] drm/i915: Remove 'prefault_disable' modparam

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 24 Jan 2020, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> The 'prefault_disable' modparam was used by IGT to prevent a few
> prefaulting operations to make fault handling under struct_mutex more
> prominent. With the removal of struct_mutex, this is not as important
> any more and we have almost completely stopped using the parameter. The
> remaining use in execbuf is now immaterial and can be dropped without
> affecting coverage.

I'll eagerly ack the removal of almost any module parameter!

Acked-by: Jani Nikula <jani.nikula@intel.com>

> We must re-address the idea of fault injection though.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Antonio Argenziano <antonio.argenziano@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 3 ---
>  drivers/gpu/drm/i915/i915_params.c             | 4 ----
>  drivers/gpu/drm/i915/i915_params.h             | 1 -
>  3 files changed, 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 60c984e10c4a..358141e1593c 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -1643,9 +1643,6 @@ static int eb_prefault_relocations(const struct i915_execbuffer *eb)
>  	const unsigned int count = eb->buffer_count;
>  	unsigned int i;
>  
> -	if (unlikely(i915_modparams.prefault_disable))
> -		return 0;
> -
>  	for (i = 0; i < count; i++) {
>  		int err;
>  
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 9c8257cf88d0..add00ec1f787 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -103,10 +103,6 @@ i915_param_named(fastboot, int, 0600,
>  	"(0=disabled, 1=enabled) "
>  	"Default: -1 (use per-chip default)");
>  
> -i915_param_named_unsafe(prefault_disable, bool, 0600,
> -	"Disable page prefaulting for pread/pwrite/reloc (default:false). "
> -	"For developers only.");
> -
>  i915_param_named_unsafe(load_detect_test, bool, 0600,
>  	"Force-enable the VGA load detect code for testing (default:false). "
>  	"For developers only.");
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index ef4069645cb8..cb16410c2ada 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -71,7 +71,6 @@ struct drm_printer;
>  	param(unsigned long, fake_lmem_start, 0, 0400) \
>  	/* leave bools at the end to not create holes */ \
>  	param(bool, enable_hangcheck, true, 0600) \
> -	param(bool, prefault_disable, false, 0600) \
>  	param(bool, load_detect_test, false, 0600) \
>  	param(bool, force_reset_modeset_test, false, 0600) \
>  	param(bool, error_capture, true, 0600) \

-- 
Jani Nikula, Intel Open Source Graphics Center
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