[PATCH] drm/qxl: size packed dumb heads from the plane source
From: Dillon Amburgey <hidden>
Date: 2026-09-24 02:53:54
Also in:
dri-devel, lkml
Subsystem:
drm driver for qxl virtual gpu, drm drivers, drm drivers and misc gpu patches, the rest · Maintainers:
Dave Airlie, Gerd Hoffmann, David Airlie, Simona Vetter, Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, Linus Torvalds
QXL packs per-CRTC dumb buffers into a single primary surface.
qxl_update_dumb_head() recorded each dumb BO allocation (bo->surf)
instead of the plane source rectangle. Scanning 1280x800 from a
2048x1024 dumb framebuffer beside a 1024x768 head therefore created
a 3072x1024 primary and placed head 1 at +2048, rather than 2304x800
with head 1 at +1280.
Use src_w/src_h when building the packed shadow, and copy only that
source rectangle into it.
Fixes: 90adda2ce898 ("drm/qxl: cover all crtcs in shadow bo.")
Assisted-by: LLM sparse
Signed-off-by: Dillon Amburgey <redacted>
---
Tested on torvalds/linux 62f4c998b297. A DRM client (not Xorg, not
SPICE) programmed one QXL device with max_outputs=2. CRTC 0 scans a
1280x800 rectangle from a 2048x1024 dumb framebuffer (the allocation
is larger than the scanout). CRTC 1 scans a separate 1024x768 dumb
framebuffer. Unpatched, qxl_update_dumb_head() sizes packed heads
from bo->surf, so QEMU's qxl_create_guest_primary is 3072x1024
(2048+1024 by max height) and monitors_config places head 1 at +2048.
With this patch, the primary is 2304x800 (1280+1024) and head 1 is at
+1280.
Content outside CRTC 0's 1280x800 source rectangle did not appear in
the packed primary, and both heads' source rectangles did.
checkpatch.pl --strict: 0 errors, 0 warnings, 0 checks. W=1 and Sparse
on drivers/gpu/drm/qxl/qxl_display.c added no warnings.
drivers/gpu/drm/qxl/qxl_display.c | 39 ++++++++++++++++---------------
1 file changed, 20 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index 0719fc6a52d5..e57aeeb97f84 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c@@ -670,13 +670,17 @@ static void qxl_primary_atomic_update(struct drm_plane *plane, struct qxl_device *qdev = to_qxl(plane->dev); struct qxl_bo *bo = gem_to_qxl_bo(new_state->fb->obj[0]); struct qxl_bo *primary; - struct drm_clip_rect norect = { - .x1 = 0, - .y1 = 0, - .x2 = new_state->fb->width, - .y2 = new_state->fb->height - }; + struct drm_clip_rect norect; uint32_t dumb_shadow_offset = 0; + u32 src_x = new_state->src_x >> 16; + u32 src_y = new_state->src_y >> 16; + u32 src_w = new_state->src_w >> 16; + u32 src_h = new_state->src_h >> 16; + + norect.x1 = src_x; + norect.y1 = src_y; + norect.x2 = src_x + src_w; + norect.y2 = src_y + src_h; primary = bo->shadow ? bo->shadow : bo;
@@ -689,7 +693,7 @@ static void qxl_primary_atomic_update(struct drm_plane *plane, if (bo->is_dumb) dumb_shadow_offset = - qdev->dumb_heads[new_state->crtc->index].x; + qdev->dumb_heads[new_state->crtc->index].x - src_x; qxl_draw_dirty_fb(qdev, new_state->fb, bo, 0, 0, &norect, 1, 1, dumb_shadow_offset);
@@ -764,18 +768,14 @@ static void qxl_cursor_atomic_disable(struct drm_plane *plane, qcrtc->cursor_bo = NULL; } -static void qxl_update_dumb_head(struct qxl_device *qdev, - int index, struct qxl_bo *bo) +static void qxl_update_dumb_head(struct qxl_device *qdev, int index, + struct qxl_bo *bo, uint32_t width, + uint32_t height) { - uint32_t width, height; - if (index >= qdev->monitors_config->max_allowed) return; - if (bo && bo->is_dumb) { - width = bo->surf.width; - height = bo->surf.height; - } else { + if (!bo || !bo->is_dumb) { width = 0; height = 0; }
@@ -820,12 +820,11 @@ static void qxl_calc_dumb_shadow(struct qxl_device *qdev, } static void qxl_prepare_shadow(struct qxl_device *qdev, struct qxl_bo *user_bo, - int crtc_index) + int crtc_index, uint32_t width, uint32_t height) { struct qxl_surface surf; - qxl_update_dumb_head(qdev, crtc_index, - user_bo); + qxl_update_dumb_head(qdev, crtc_index, user_bo, width, height); qxl_calc_dumb_shadow(qdev, &surf); if (!qdev->dumb_shadow_bo || qdev->dumb_shadow_bo->surf.width != surf.width ||
@@ -869,7 +868,9 @@ static int qxl_plane_prepare_fb(struct drm_plane *plane, if (plane->type == DRM_PLANE_TYPE_PRIMARY && user_bo->is_dumb) { - qxl_prepare_shadow(qdev, user_bo, new_state->crtc->index); + qxl_prepare_shadow(qdev, user_bo, new_state->crtc->index, + new_state->src_w >> 16, + new_state->src_h >> 16); } if (plane->type == DRM_PLANE_TYPE_CURSOR &&
base-commit: 62f4c998b297cf233997a2b4cd6fc2d2df0319c9 -- 2.43.0