virtio-gpu: splitting one extended mode guest fb into n-scanouts

When guest is running Linux/X11 with extended multiple displays mode enabled,
the guest shares one scanout resource each time containing whole surface
rather than sharing individual display output separately. This extended frame
is properly splited and rendered on the corresponding scanout surfaces but
not in case of blob-resource (zero copy).

This code change lets the qemu split this one large surface data into multiple
in case of blob-resource as well so that each sub frame then can be blitted
properly to each scanout.

v2: resizing qemu console in virtio_gpu_update_dmabuf to scanout's width and
    height

v3: updating stub function of virtio_gpu_update_dmabuf to match the type

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Message-Id: <20211104065153.28897-5-dongwon.kim@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/virtio-gpu-udmabuf-stubs.c

@@ -20,7 +20,8 @@ void virtio_gpu_fini_udmabuf(struct virtio_gpu_simple_resource *res)
 int virtio_gpu_update_dmabuf(VirtIOGPU *g,
                              uint32_t scanout_id,
                              struct virtio_gpu_simple_resource *res,
-                             struct virtio_gpu_framebuffer *fb)
+                             struct virtio_gpu_framebuffer *fb,
+                             struct virtio_gpu_rect *r)
 {
     /* nothing (stub) */
     return 0;

hw/display/virtio-gpu-udmabuf.c

@@ -171,7 +171,8 @@ static VGPUDMABuf
 *virtio_gpu_create_dmabuf(VirtIOGPU *g,
                           uint32_t scanout_id,
                           struct virtio_gpu_simple_resource *res,
-                          struct virtio_gpu_framebuffer *fb)
+                          struct virtio_gpu_framebuffer *fb,
+                          struct virtio_gpu_rect *r)
 {
     VGPUDMABuf *dmabuf;
 
@@ -183,6 +184,10 @@ static VGPUDMABuf
     dmabuf->buf.width = fb->width;
     dmabuf->buf.height = fb->height;
     dmabuf->buf.stride = fb->stride;
+    dmabuf->buf.x = r->x;
+    dmabuf->buf.y = r->y;
+    dmabuf->buf.scanout_width = r->width;
+    dmabuf->buf.scanout_height = r->height;
     dmabuf->buf.fourcc = qemu_pixman_to_drm_format(fb->format);
     dmabuf->buf.fd = res->dmabuf_fd;
     dmabuf->buf.allow_fences = true;
@@ -196,24 +201,25 @@ static VGPUDMABuf
 int virtio_gpu_update_dmabuf(VirtIOGPU *g,
                              uint32_t scanout_id,
                              struct virtio_gpu_simple_resource *res,
-                             struct virtio_gpu_framebuffer *fb)
+                             struct virtio_gpu_framebuffer *fb,
+                             struct virtio_gpu_rect *r)
 {
     struct virtio_gpu_scanout *scanout = &g->parent_obj.scanout[scanout_id];
     VGPUDMABuf *new_primary, *old_primary = NULL;
 
-    new_primary = virtio_gpu_create_dmabuf(g, scanout_id, res, fb);
+    new_primary = virtio_gpu_create_dmabuf(g, scanout_id, res, fb, r);
     if (!new_primary) {
         return -EINVAL;
     }
 
-    if (g->dmabuf.primary) {
-        old_primary = g->dmabuf.primary;
+    if (g->dmabuf.primary[scanout_id]) {
+        old_primary = g->dmabuf.primary[scanout_id];
     }
 
-    g->dmabuf.primary = new_primary;
+    g->dmabuf.primary[scanout_id] = new_primary;
     qemu_console_resize(scanout->con,
-                        new_primary->buf.width,
-                        new_primary->buf.height);
+                        new_primary->buf.scanout_width,
+                        new_primary->buf.scanout_height);
     dpy_gl_scanout_dmabuf(scanout->con, &new_primary->buf);
 
     if (old_primary) {

hw/display/virtio-gpu.c

@@ -517,9 +517,9 @@ static void virtio_gpu_resource_flush(VirtIOGPU *g,
                 console_has_gl(scanout->con)) {
                 dpy_gl_update(scanout->con, 0, 0, scanout->width,
                               scanout->height);
-                return;
             }
         }
+        return;
     }
 
     if (!res->blob &&
@@ -627,7 +627,7 @@ static void virtio_gpu_do_set_scanout(VirtIOGPU *g,
 
     if (res->blob) {
         if (console_has_gl(scanout->con)) {
-            if (!virtio_gpu_update_dmabuf(g, scanout_id, res, fb)) {
+            if (!virtio_gpu_update_dmabuf(g, scanout_id, res, fb, r)) {
                 virtio_gpu_update_scanout(g, scanout_id, res, r);
                 return;
             }

include/hw/virtio/virtio-gpu.h

@@ -187,7 +187,7 @@ struct VirtIOGPU {
 
     struct {
         QTAILQ_HEAD(, VGPUDMABuf) bufs;
-        VGPUDMABuf *primary;
+        VGPUDMABuf *primary[VIRTIO_GPU_MAX_SCANOUTS];
     } dmabuf;
 };
 
@@ -273,7 +273,8 @@ void virtio_gpu_fini_udmabuf(struct virtio_gpu_simple_resource *res);
 int virtio_gpu_update_dmabuf(VirtIOGPU *g,
                              uint32_t scanout_id,
                              struct virtio_gpu_simple_resource *res,
-                             struct virtio_gpu_framebuffer *fb);
+                             struct virtio_gpu_framebuffer *fb,
+                             struct virtio_gpu_rect *r);
 
 /* virtio-gpu-3d.c */
 void virtio_gpu_virgl_process_cmd(VirtIOGPU *g,

include/ui/console.h

@@ -167,6 +167,10 @@ typedef struct QemuDmaBuf {
     uint32_t  fourcc;
     uint64_t  modifier;
     uint32_t  texture;
+    uint32_t  x;
+    uint32_t  y;
+    uint32_t  scanout_width;
+    uint32_t  scanout_height;
     bool      y0_top;
     void      *sync;
     int       fence_fd;