tu: Allow being preempted on a7xx

This is only tested on a7xx so far, although it should work on a6xx too.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30544>

src/freedreno/vulkan/tu_device.h

@@ -124,6 +124,8 @@ struct tu_physical_device
    bool has_cached_non_coherent_memory;
    uintptr_t level1_dcache_size;
 
+   bool has_preemption;
+
    struct {
       uint32_t type_count;
       VkMemoryPropertyFlags types[VK_MAX_MEMORY_TYPES];

src/freedreno/vulkan/tu_knl_drm_msm.cc

@@ -121,6 +121,24 @@ tu_drm_get_va_prop(const struct tu_physical_device *dev,
    return 0;
 }
 
+static bool
+tu_drm_has_preemption(const struct tu_physical_device *dev)
+{
+   struct drm_msm_submitqueue req = {
+      .flags = MSM_SUBMITQUEUE_ALLOW_PREEMPT,
+      .prio = dev->submitqueue_priority_count / 2,
+   };
+
+   int ret = drmCommandWriteRead(dev->local_fd,
+                                 DRM_MSM_SUBMITQUEUE_NEW, &req, sizeof(req));
+   if (ret)
+      return false;
+
+   drmCommandWrite(dev->local_fd, DRM_MSM_SUBMITQUEUE_CLOSE, &req.id,
+                   sizeof(req.id));
+   return true;
+}
+
 static uint32_t
 tu_drm_get_priorities(const struct tu_physical_device *dev)
 {
@@ -214,7 +232,9 @@ msm_submitqueue_new(struct tu_device *dev,
    assert(priority >= 0 &&
           priority < dev->physical_device->submitqueue_priority_count);
    struct drm_msm_submitqueue req = {
-      .flags = 0,
+      .flags = dev->physical_device->info->chip >= 7 &&
+         dev->physical_device->has_preemption ?
+         MSM_SUBMITQUEUE_ALLOW_PREEMPT : 0,
       .prio = priority,
    };
 
@@ -1245,6 +1265,8 @@ tu_knl_drm_msm_load(struct tu_instance *instance,
    device->has_set_iova = !tu_drm_get_va_prop(device, &device->va_start,
                                               &device->va_size);
 
+   device->has_preemption = tu_drm_has_preemption(device);
+
    /* Even if kernel is new enough, the GPU itself may not support it. */
    device->has_cached_coherent_memory =
       (device->msm_minor_version >= 8) &&

src/freedreno/vulkan/tu_knl_drm_virtio.cc

@@ -310,11 +310,13 @@ virtio_submitqueue_new(struct tu_device *dev,
           priority < dev->physical_device->submitqueue_priority_count);
 
    struct drm_msm_submitqueue req = {
-      .flags = 0,
+      .flags = dev->physical_device->info->chip >= 7 &&
+         dev->physical_device->has_preemption ?
+         MSM_SUBMITQUEUE_ALLOW_PREEMPT : 0,
       .prio = priority,
    };
 
-   int ret = virtio_simple_ioctl(dev, DRM_IOCTL_MSM_SUBMITQUEUE_NEW, &req);
+   int ret = virtio_simple_ioctl(dev->vdev->vdrm, DRM_IOCTL_MSM_SUBMITQUEUE_NEW, &req);
    if (ret)
       return ret;
 
@@ -328,6 +330,22 @@ virtio_submitqueue_close(struct tu_device *dev, uint32_t queue_id)
    virtio_simple_ioctl(dev->vdev->vdrm, DRM_IOCTL_MSM_SUBMITQUEUE_CLOSE, &queue_id);
 }
 
+static bool
+virtio_has_preemption(struct vdrm_device *vdrm)
+{
+   struct drm_msm_submitqueue req = {
+      .flags = MSM_SUBMITQUEUE_ALLOW_PREEMPT,
+      .prio = vdrm->caps.u.msm.priorities / 2,
+   };
+
+   int ret = virtio_simple_ioctl(vdrm, DRM_IOCTL_MSM_SUBMITQUEUE_NEW, &req);
+   if (ret)
+      return false;
+
+   virtio_simple_ioctl(vdrm, DRM_IOCTL_MSM_SUBMITQUEUE_CLOSE, &req.id);
+   return true;
+}
+
 static VkResult
 tu_wait_fence(struct tu_device *dev,
               uint32_t queue_id,
@@ -1312,6 +1330,11 @@ tu_knl_drm_virtio_load(struct tu_instance *instance,
 
    caps = vdrm->caps;
 
+   /* TODO add something to virgl_renderer_capset_drm to avoid round-trip to
+    * host if virglrenderer is new enough.
+    */
+   bool has_preemption = virtio_has_preemption(vdrm);
+
    vdrm_device_close(vdrm);
 
    mesa_logd("wire_format_version: %u", caps.wire_format_version);
@@ -1367,6 +1390,7 @@ tu_knl_drm_virtio_load(struct tu_instance *instance,
    device->va_start       = caps.u.msm.va_start;
    device->va_size        = caps.u.msm.va_size;
    device->has_set_iova   = true;
+   device->has_preemption = has_preemption;
 
    device->gmem_size = debug_get_num_option("TU_GMEM", device->gmem_size);
 

src/freedreno/vulkan/tu_knl_kgsl.cc

@@ -1596,6 +1596,9 @@ tu_knl_kgsl_load(struct tu_instance *instance, int fd)
       fd, KGSL_MEMFLAGS_IOCOHERENT |
              (KGSL_CACHEMODE_WRITEBACK << KGSL_CACHEMODE_SHIFT));
 
+   /* preemption is always supported on kgsl */
+   device->has_preemption = true;
+
    instance->knl = &kgsl_knl_funcs;
 
    result = tu_physical_device_init(device, instance);