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@xxxxxxxxxx/ 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. 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 | 12 +++ 3 files changed, 159 insertions(+), 7 deletions(-) base-commit: f24d1d4a7a425e67551ca8d86a89df7102766ac9 -- 2.47.1
