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Message-ID: <20250407140138.162383-1-jfalempe@redhat.com>
Date: Mon, 7 Apr 2025 15:42:24 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>,
Ryosuke Yasuoka <ryasuoka@...hat.com>,
Javier Martinez Canillas <javierm@...hat.com>,
Wei Yang <richard.weiyang@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>,
John Ogness <john.ogness@...utronix.de>,
Thomas Gleixner <tglx@...utronix.de>,
linux-mm@...ck.org,
dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Cc: Jocelyn Falempe <jfalempe@...hat.com>
Subject: [PATCH v3 0/2] drm/panic: Add support to scanout buffer as array of pages
Some drivers like virtio-gpu, don't map the scanout buffer in the
kernel. Calling vmap() in a panic handler is not safe, and writing an
atomic_vmap() API is more complex than expected [1].
So instead, pass the array of pages of the scanout buffer to the
panic handler, and map only one page at a time to draw the pixels.
This is obviously slow, but acceptable for a panic handler.
As kmap_local_page() is not safe to call from a panic handler,
introduce a kmap_local_page_try_from_panic() that will avoid unsafe
operations.
[1] https://lore.kernel.org/dri-devel/20250305152555.318159-1-ryasuoka@redhat.com/
v2:
* Add kmap_local_page_try_from_panic() (Simona Vetter)
* Correctly handle the case if kmap_local_page_try_from_panic()
returns NULL
* Check that the current page is not NULL before trying to map it.
* Add a comment in struct drm_scanout_buffer, that the array of
pages shouldn't be allocated in the get_scanout_buffer() callback.
v3:
* Replace DRM_WARN_ONCE with pr_debug_once (Simona Vetter)
* Add a comment in kmap_local_page_try_from_panic() (Thomas Gleixner)
Jocelyn Falempe (2):
mm/kmap: Add kmap_local_page_try_from_panic()
drm/panic: Add support to scanout buffer as array of pages
drivers/gpu/drm/drm_panic.c | 142 +++++++++++++++++++++++++++++--
include/drm/drm_panic.h | 12 ++-
include/linux/highmem-internal.h | 13 +++
3 files changed, 160 insertions(+), 7 deletions(-)
base-commit: fbe43810d563a293e3de301141d33caf1f5d5c5a
--
2.49.0
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