[PATCH v2 11/14] virtio-gpu: refactor async blob unmapping

["Alex Bennée" <alex.bennee@linaro.org>]

From: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>

Change the 3 part async cleanup of a blob memory mapping to check if the
unmapping has finished already after deleting the subregion; this
condition allows us to skip suspending the command and responding to the
guest right away.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20250410122643.1747913-4-manos.pitsidianakis@linaro.org>
Cc: qemu-stable@nongnu.org
---
 hw/display/virtio-gpu-virgl.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
index 8fbe4e70cc..32a32879f7 100644
--- a/hw/display/virtio-gpu-virgl.c
+++ b/hw/display/virtio-gpu-virgl.c
@@ -155,7 +155,32 @@ virtio_gpu_virgl_unmap_resource_blob(VirtIOGPU *g,
      *    asynchronously by virtio_gpu_virgl_hostmem_region_free().
      * 3. Finish the unmapping with final virgl_renderer_resource_unmap().
      */
+
+    /* 1. Check if we should start unmapping now */
+    if (!vmr->finish_unmapping) {
+        /* begin async unmapping. render will be unblocked once MR is freed */
+        b->renderer_blocked++;
+
+        memory_region_set_enabled(mr, false);
+        memory_region_del_subregion(&b->hostmem, mr);
+        object_unparent(OBJECT(mr));
+        /*
+         * The unmapping might have already finished at this point if no one
+         * else held a reference to the MR; if yes, we can skip suspending the
+         * command and unmap the resource right away.
+         */
+        *cmd_suspended = !vmr->finish_unmapping;
+    }
+
+    /*
+     * 2. if virtio_gpu_virgl_hostmem_region_free hasn't been executed yet, we
+     * have marked the command to be re-processed later by setting
+     * cmd_suspended to true. The freeing callback will be called from RCU
+     * context later.
+     */
+
     if (vmr->finish_unmapping) {
+        /* 3. MemoryRegion has been freed, so finish unmapping */
         res->mr = NULL;
         g_free(vmr);
 
@@ -166,16 +191,6 @@ virtio_gpu_virgl_unmap_resource_blob(VirtIOGPU *g,
                           __func__, strerror(-ret));
             return ret;
         }
-    } else {
-        *cmd_suspended = true;
-
-        /* render will be unblocked once MR is freed */
-        b->renderer_blocked++;
-
-        /* memory region owns self res->mr object and frees it by itself */
-        memory_region_set_enabled(mr, false);
-        memory_region_del_subregion(&b->hostmem, mr);
-        object_unparent(OBJECT(mr));
     }
 
     return 0;
-- 
2.39.5