radeon: Support shared memory user pointers.

The RADEON_GEM_USERPTR_ANONONLY flag is hardcoded here which excludes
shared memory pages. DRM is actually capable of supporting shared file-
backed memory, but only if it's read-only. This mutability intent has to
be conveyed through the stack, so a flags argument is added to the winsys
regime to pass RADEON_FLAG_READ_ONLY.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16115>

src/gallium/drivers/r600/r600_buffer_common.c

@@ -656,7 +656,8 @@ r600_buffer_from_user_memory(struct pipe_screen *screen,
 	util_range_add(&rbuffer->b.b, &rbuffer->b.valid_buffer_range, 0, templ->width0);
 
 	/* Convert a user pointer to a buffer. */
-	rbuffer->buf = ws->buffer_from_ptr(ws, user_memory, templ->width0);
+	rbuffer->buf = ws->buffer_from_ptr(ws, user_memory, templ->width0,
+	                                   templ->usage == PIPE_USAGE_IMMUTABLE? RADEON_FLAG_READ_ONLY : 0);
 	if (!rbuffer->buf) {
 		FREE(rbuffer);
 		return NULL;

src/gallium/drivers/radeonsi/si_buffer.c

@@ -650,7 +650,7 @@ static struct pipe_resource *si_buffer_from_user_memory(struct pipe_screen *scre
    buf->b.buffer_id_unique = util_idalloc_mt_alloc(&sscreen->buffer_ids);
 
    /* Convert a user pointer to a buffer. */
-   buf->buf = ws->buffer_from_ptr(ws, user_memory, templ->width0);
+   buf->buf = ws->buffer_from_ptr(ws, user_memory, templ->width0, 0);
    if (!buf->buf) {
       si_resource_destroy(screen, &buf->b.b);
       return NULL;

src/gallium/include/winsys/radeon_winsys.h

@@ -388,7 +388,7 @@ struct radeon_winsys {
     * \param pointer   User pointer to turn into a buffer object.
     * \param Size      Size in bytes for the new buffer.
     */
-   struct pb_buffer *(*buffer_from_ptr)(struct radeon_winsys *ws, void *pointer, uint64_t size);
+   struct pb_buffer *(*buffer_from_ptr)(struct radeon_winsys *ws, void *pointer, uint64_t size, enum radeon_bo_flag flags);
 
    /**
     * Whether the buffer was created from a user pointer.

src/gallium/winsys/amdgpu/drm/amdgpu_bo.c

@@ -1660,7 +1660,8 @@ static bool amdgpu_bo_get_handle(struct radeon_winsys *rws,
 }
 
 static struct pb_buffer *amdgpu_bo_from_ptr(struct radeon_winsys *rws,
-					    void *pointer, uint64_t size)
+					    void *pointer, uint64_t size,
+					    enum radeon_bo_flag flags)
 {
     struct amdgpu_winsys *ws = amdgpu_winsys(rws);
     amdgpu_bo_handle buf_handle;

src/gallium/winsys/radeon/drm/radeon_drm_bo.c

@@ -1089,7 +1089,8 @@ radeon_winsys_bo_create(struct radeon_winsys *rws,
 }
 
 static struct pb_buffer *radeon_winsys_bo_from_ptr(struct radeon_winsys *rws,
-                                                   void *pointer, uint64_t size)
+                                                   void *pointer, uint64_t size,
+                                                   enum radeon_bo_flag flags)
 {
    struct radeon_drm_winsys *ws = radeon_drm_winsys(rws);
    struct drm_radeon_gem_userptr args;
@@ -1103,9 +1104,15 @@ static struct pb_buffer *radeon_winsys_bo_from_ptr(struct radeon_winsys *rws,
    memset(&args, 0, sizeof(args));
    args.addr = (uintptr_t)pointer;
    args.size = align(size, ws->info.gart_page_size);
-   args.flags = RADEON_GEM_USERPTR_ANONONLY |
-                RADEON_GEM_USERPTR_VALIDATE |
-                RADEON_GEM_USERPTR_REGISTER;
+
+   if (flags & RADEON_FLAG_READ_ONLY)
+      args.flags = RADEON_GEM_USERPTR_READONLY |
+                   RADEON_GEM_USERPTR_VALIDATE;
+   else
+      args.flags = RADEON_GEM_USERPTR_ANONONLY |
+                   RADEON_GEM_USERPTR_REGISTER |
+                   RADEON_GEM_USERPTR_VALIDATE;
+
    if (drmCommandWriteRead(ws->fd, DRM_RADEON_GEM_USERPTR,
                            &args, sizeof(args))) {
       FREE(bo);