venus: initialize physical devices once

Avoid re-enumeration when there is no device or no supported device.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Ryan Neph <ryanneph@google.com>
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12653>

src/virtio/vulkan/vn_instance.c

@@ -778,7 +778,7 @@ vn_DestroyInstance(VkInstance _instance,
    if (!instance)
       return;
 
-   if (instance->physical_device.devices) {
+   if (instance->physical_device.initialized) {
       for (uint32_t i = 0; i < instance->physical_device.device_count; i++)
          vn_physical_device_fini(&instance->physical_device.devices[i]);
       vk_free(alloc, instance->physical_device.devices);

src/virtio/vulkan/vn_instance.h

@@ -73,6 +73,7 @@ struct vn_instance {
 
    struct {
       mtx_t mutex;
+      bool initialized;
 
       struct vn_physical_device *devices;
       uint32_t device_count;

src/virtio/vulkan/vn_physical_device.c

@@ -1267,10 +1267,11 @@ vn_instance_enumerate_physical_devices(struct vn_instance *instance)
 
    mtx_lock(&instance->physical_device.mutex);
 
-   if (instance->physical_device.devices) {
+   if (instance->physical_device.initialized) {
       result = VK_SUCCESS;
       goto out;
    }
+   instance->physical_device.initialized = true;
 
    uint32_t count;
    result = vn_call_vkEnumeratePhysicalDevices(