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.
[1] https://lore.kernel.org/dri-devel/20250305152555.318159-1-ryasu...@redhat.com/ Signed-off-by: Jocelyn Falempe <jfale...@redhat.com> --- drivers/gpu/drm/drm_panic.c | 139 ++++++++++++++++++++++++++++++++++-- include/drm/drm_panic.h | 10 ++- 2 files changed, 142 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c index ab42a2b1567d..e10ab8fe847c 100644 --- a/drivers/gpu/drm/drm_panic.c +++ b/drivers/gpu/drm/drm_panic.c @@ -7,6 +7,7 @@ */ #include <linux/font.h> +#include <linux/highmem.h> #include <linux/init.h> #include <linux/iosys-map.h> #include <linux/kdebug.h> @@ -154,6 +155,87 @@ static void drm_panic_blit_pixel(struct drm_scanout_buffer *sb, struct drm_rect sb->set_pixel(sb, clip->x1 + x, clip->y1 + y, fg_color); } +static void drm_panic_write_pixel16(void *vaddr, unsigned int offset, u16 color) +{ + u16 *p = vaddr + offset; + + *p = color; +} + +static void drm_panic_write_pixel24(void *vaddr, unsigned int offset, u32 color) +{ + u8 *p = vaddr + offset; + + *p++ = color & 0xff; + color >>= 8; + *p++ = color & 0xff; + color >>= 8; + *p = color & 0xff; +} + +static void drm_panic_write_pixel32(void *vaddr, unsigned int offset, u32 color) +{ + u32 *p = vaddr + offset; + + *p = color; +} + +static void drm_panic_write_pixel(void *vaddr, unsigned int offset, u32 color, unsigned int cpp) +{ + switch (cpp) { + case 2: + drm_panic_write_pixel16(vaddr, offset, color); + break; + case 3: + drm_panic_write_pixel24(vaddr, offset, color); + break; + case 4: + drm_panic_write_pixel32(vaddr, offset, color); + break; + default: + DRM_WARN_ONCE("Can't blit with pixel width %d\n", cpp); + } +} + +/* + * The scanout buffer pages are not mapped, so for each pixel, + * use kmap_local_page() to map the page, and write the pixel. + * Tries to keep the map from the previous pixel, to avoid too much map/unmap. + */ +static void drm_panic_blit_page(struct page **pages, unsigned int dpitch, + unsigned int cpp, const u8 *sbuf8, + unsigned int spitch, struct drm_rect *clip, + unsigned int scale, u32 fg32) +{ + unsigned int y, x; + unsigned int page = ~0; + unsigned int height = drm_rect_height(clip); + unsigned int width = drm_rect_width(clip); + void *vaddr = NULL; + + for (y = 0; y < height; y++) { + for (x = 0; x < width; x++) { + if (drm_draw_is_pixel_fg(sbuf8, spitch, x / scale, y / scale)) { + unsigned int new_page; + unsigned int offset; + + offset = (y + clip->y1) * dpitch + (x + clip->x1) * cpp; + new_page = offset >> PAGE_SHIFT; + offset = offset % PAGE_SIZE; + if (new_page != page) { + if (vaddr) + kunmap_local(vaddr); + page = new_page; + vaddr = kmap_local_page(pages[page]); + } + drm_panic_write_pixel(vaddr, offset, fg32, cpp); + } + } + } + if (vaddr) + kunmap_local(vaddr); +} + /* * drm_panic_blit - convert a monochrome image to a linear framebuffer * @sb: destination scanout buffer @@ -177,6 +259,10 @@ static void drm_panic_blit(struct drm_scanout_buffer *sb, struct drm_rect *clip, if (sb->set_pixel) return drm_panic_blit_pixel(sb, clip, sbuf8, spitch, scale, fg_color); + if (sb->pages) + return drm_panic_blit_page(sb->pages, sb->pitch[0], sb->format->cpp[0], + sbuf8, spitch, clip, scale, fg_color); + map = sb->map[0]; iosys_map_incr(&map, clip->y1 * sb->pitch[0] + clip->x1 * sb->format->cpp[0]); @@ -209,6 +295,35 @@ static void drm_panic_fill_pixel(struct drm_scanout_buffer *sb, sb->set_pixel(sb, clip->x1 + x, clip->y1 + y, color); } +static void drm_panic_fill_page(struct page **pages, unsigned int dpitch, + unsigned int cpp, struct drm_rect *clip, + u32 color) +{ + unsigned int y, x; + unsigned int page = ~0; + void *vaddr = NULL; + + for (y = clip->y1; y < clip->y2; y++) { + for (x = clip->x1; x < clip->x2; x++) { + unsigned int new_page; + unsigned int offset; + + offset = y * dpitch + x * cpp; + new_page = offset >> PAGE_SHIFT; + offset = offset % PAGE_SIZE; + if (new_page != page) { + if (vaddr) + kunmap_local(vaddr); + page = new_page; + vaddr = kmap_local_page(pages[page]); + } + drm_panic_write_pixel(vaddr, offset, color, cpp); + } + } + if (vaddr) + kunmap_local(vaddr); +} + /* * drm_panic_fill - Fill a rectangle with a color * @sb: destination scanout buffer @@ -225,6 +340,10 @@ static void drm_panic_fill(struct drm_scanout_buffer *sb, struct drm_rect *clip, if (sb->set_pixel) return drm_panic_fill_pixel(sb, clip, color); + if (sb->pages) + return drm_panic_fill_page(sb->pages, sb->pitch[0], sb->format->cpp[0], + clip, color); + map = sb->map[0]; iosys_map_incr(&map, clip->y1 * sb->pitch[0] + clip->x1 * sb->format->cpp[0]); @@ -714,16 +833,24 @@ static void draw_panic_plane(struct drm_plane *plane, const char *description) if (!drm_panic_trylock(plane->dev, flags)) return; + ret = plane->helper_private->get_scanout_buffer(plane, &sb); + + if (ret || !drm_panic_is_format_supported(sb.format)) + goto unlock; + + /* One of these should be set, or it can't draw pixels */ + if (!sb.set_pixel && !sb.pages && iosys_map_is_null(&sb.map[0])) + goto unlock; + drm_panic_set_description(description); - ret = plane->helper_private->get_scanout_buffer(plane, &sb); + draw_panic_dispatch(&sb); + if (plane->helper_private->panic_flush) + plane->helper_private->panic_flush(plane); - if (!ret && drm_panic_is_format_supported(sb.format)) { - draw_panic_dispatch(&sb); - if (plane->helper_private->panic_flush) - plane->helper_private->panic_flush(plane); - } drm_panic_clear_description(); + +unlock: drm_panic_unlock(plane->dev, flags); } diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h index f4e1fa9ae607..8b91a13347b9 100644 --- a/include/drm/drm_panic.h +++ b/include/drm/drm_panic.h @@ -39,6 +39,14 @@ struct drm_scanout_buffer { */ struct iosys_map map[DRM_FORMAT_MAX_PLANES]; + /** + * @pages: Optional, if the scanout buffer is not mapped, set this field + * to the array of pages of the scanout buffer. The panic code will use + * kmap_local_page() to map one page at a time to write all the pixels. + * The scanout buffer should be in linear format. + */ + struct page **pages; + /** * @width: Width of the scanout buffer, in pixels. */ @@ -57,7 +65,7 @@ struct drm_scanout_buffer { /** * @set_pixel: Optional function, to set a pixel color on the * framebuffer. It allows to handle special tiling format inside the - * driver. + * driver. It takes precedence over the @map and @pages fields. */ void (*set_pixel)(struct drm_scanout_buffer *sb, unsigned int x, unsigned int y, u32 color); base-commit: 9e75b6ef407fee5d4ed8021cd7ddd9d6a8f7b0e8 -- 2.47.1
