linux-kernel - Re: [PATCH] gpu/drm: Use local kmap in drm_clflush

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Message-ID: <20251208004002.wgjjpbkf3ch3h4xb@offworld>
Date: Sun, 7 Dec 2025 16:40:02 -0800
From: Davidlohr Bueso <dave@...olabs.net>
To: maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
	tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpu/drm: Use local kmap in drm_clflush_page()

ping?

On Mon, 17 Nov 2025, Davidlohr Bueso wrote:

>Replace the now deprecated kmap_atomic() with kmap_local_page().
>
>Optimize for the non-highmem cases and avoid disabling preemption and
>pagefaults as clflushopt does not require being CPU locality guarantees
>and the mapping will hold valid across context switches. Further, highmem
>is planned to to be removed[1].
>
>[1] https://lore.kernel.org/all/4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com/
>Signed-off-by: Davidlohr Bueso <dave@...olabs.net>
>---
> drivers/gpu/drm/drm_cache.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c
>index ea1d2d5d2c66..b6a309f827f8 100644
>--- a/drivers/gpu/drm/drm_cache.c
>+++ b/drivers/gpu/drm/drm_cache.c
>@@ -57,10 +57,10 @@ drm_clflush_page(struct page *page)
> 	if (unlikely(page == NULL))
> 		return;
>
>-	page_virtual = kmap_atomic(page);
>+	page_virtual = kmap_local_page(page);
> 	for (i = 0; i < PAGE_SIZE; i += size)
> 		clflushopt(page_virtual + i);
>-	kunmap_atomic(page_virtual);
>+	kunmap_local(page_virtual);
> }
>
> static void drm_cache_flush_clflush(struct page *pages[],
>-- 
>2.39.5
>