linux-kernel - Re: [PATCH 07/11] drm/i915: stop using kmap in i915_gem_object

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Message-ID: <8d318fcb-f472-85ed-6639-18f9c45f30e4@linux.intel.com>
Date:   Fri, 25 Sep 2020 14:01:59 +0100
From:   Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Minchan Kim <minchan@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Nitin Gupta <ngupta@...are.org>, x86@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 07/11] drm/i915: stop using kmap in i915_gem_object_map


On 24/09/2020 14:58, Christoph Hellwig wrote:
> kmap for !PageHighmem is just a convoluted way to say page_address,
> and kunmap is a no-op in that case.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_pages.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index d6eeefab3d018b..6550c0bc824ea2 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -162,8 +162,6 @@ static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
>   {
>   	if (is_vmalloc_addr(ptr))
>   		vunmap(ptr);
> -	else
> -		kunmap(kmap_to_page(ptr));
>   }
>   
>   struct sg_table *
> @@ -277,11 +275,10 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
>   		 * forever.
>   		 *
>   		 * So if the page is beyond the 32b boundary, make an explicit
> -		 * vmap. On 64b, this check will be optimised away as we can
> -		 * directly kmap any page on the system.
> +		 * vmap.
>   		 */
>   		if (!PageHighMem(page))
> -			return kmap(page);
> +			return page_address(page);
>   	}
>   
>   	mem = stack;
> 

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

Regards,

Tvrtko