venus: populate oom from ring submit alloc failures

ring_seqno_valid indicates a successful ring cmd submission, and can be
used to avoid invalid reply decoding due to failed submit alloc.
Otherwise, the garbled VkResult will mislead into initialization failure
instead of oom.

Below cts failure is fixed:
dEQP-VK.api.device_init.create_instance_device_intentional_alloc_fail.basic

Fixes: ec131c6e55 ("venus: use instance allocator for ring allocs")
Signed-off-by: Yiwei Zhang <zzyiwei@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27026>

src/virtio/vulkan/vn_ring.c

@@ -633,7 +633,6 @@ vn_ring_submit_command(struct vn_ring *ring,
    vn_cs_encoder_commit(&submit->command);
 
    size_t reply_offset = 0;
-   submit->reply_shmem = NULL;
    if (submit->reply_size) {
       submit->reply_shmem = vn_instance_reply_shmem_alloc(
          ring->instance, submit->reply_size, &reply_offset);
@@ -653,11 +652,16 @@ vn_ring_submit_command(struct vn_ring *ring,
    mtx_unlock(&ring->mutex);
 
    if (submit->reply_size) {
-      void *reply_ptr = submit->reply_shmem->mmap_ptr + reply_offset;
-      submit->reply =
-         VN_CS_DECODER_INITIALIZER(reply_ptr, submit->reply_size);
-      if (submit->ring_seqno_valid)
+      if (likely(submit->ring_seqno_valid)) {
+         void *reply_ptr = submit->reply_shmem->mmap_ptr + reply_offset;
+         submit->reply =
+            VN_CS_DECODER_INITIALIZER(reply_ptr, submit->reply_size);
          vn_ring_wait_seqno(ring, submit->ring_seqno);
+      } else {
+         vn_renderer_shmem_unref(ring->instance->renderer,
+                                 submit->reply_shmem);
+         submit->reply_shmem = NULL;
+      }
    }
 }
 

src/virtio/vulkan/vn_ring.h

@@ -77,7 +77,7 @@ struct vn_ring_submit_command {
    struct vn_renderer_shmem *reply_shmem;
    struct vn_cs_decoder reply;
 
-   /* valid when instance ring submission succeeds */
+   /* valid when ring submission succeeds */
    bool ring_seqno_valid;
    uint32_t ring_seqno;
 };
@@ -95,6 +95,8 @@ vn_ring_submit_command_init(struct vn_ring *ring,
    submit->reply_size = reply_size;
    submit->reply_shmem = NULL;
 
+   submit->ring_seqno_valid = false;
+
    return &submit->command;
 }