iris: Add a new IRIS_MMAP_NONE map type

This indicates that the buffer can never be mapped.  We use this
primarily for imported BOs.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11888>

src/gallium/drivers/iris/iris_bufmgr.c

@@ -801,7 +801,7 @@ iris_bo_gem_create_from_name(struct iris_bufmgr *bufmgr,
    bo->global_name = handle;
    bo->reusable = false;
    bo->imported = true;
-   bo->mmap_mode = IRIS_MMAP_WC;
+   bo->mmap_mode = IRIS_MMAP_NONE;
    bo->kflags = EXEC_OBJECT_SUPPORTS_48B_ADDRESS | EXEC_OBJECT_PINNED;
    bo->address = vma_alloc(bufmgr, IRIS_MEMZONE_OTHER, bo->size, 1);
 
@@ -1051,6 +1051,7 @@ iris_bo_gem_mmap_offset(struct pipe_debug_callback *dbg, struct iris_bo *bo)
       [IRIS_MMAP_WC]    = I915_MMAP_OFFSET_WC,
       [IRIS_MMAP_WB]    = I915_MMAP_OFFSET_WB,
    };
+   assert(bo->mmap_mode != IRIS_MMAP_NONE);
    assert(bo->mmap_mode < ARRAY_SIZE(mmap_offset_for_mode));
    mmap_arg.flags = mmap_offset_for_mode[bo->mmap_mode];
 
@@ -1080,6 +1081,10 @@ iris_bo_map(struct pipe_debug_callback *dbg,
 {
    struct iris_bufmgr *bufmgr = bo->bufmgr;
 
+   assert(bo->mmap_mode != IRIS_MMAP_NONE);
+   if (bo->mmap_mode == IRIS_MMAP_NONE)
+      return NULL;
+
    if (!bo->map) {
       DBG("iris_bo_map: %d (%s)\n", bo->gem_handle, bo->name);
       void *map = bufmgr->has_mmap_offset ? iris_bo_gem_mmap_offset(dbg, bo)
@@ -1306,7 +1311,7 @@ iris_bo_import_dmabuf(struct iris_bufmgr *bufmgr, int prime_fd)
    bo->name = "prime";
    bo->reusable = false;
    bo->imported = true;
-   bo->mmap_mode = IRIS_MMAP_WC;
+   bo->mmap_mode = IRIS_MMAP_NONE;
    bo->kflags = EXEC_OBJECT_SUPPORTS_48B_ADDRESS | EXEC_OBJECT_PINNED;
 
    /* From the Bspec, Memory Compression - Gfx12:

src/gallium/drivers/iris/iris_bufmgr.h

@@ -123,6 +123,7 @@ iris_domain_is_read_only(enum iris_domain access)
 }
 
 enum iris_mmap_mode {
+   IRIS_MMAP_NONE, /**< Cannot be mapped */
    IRIS_MMAP_UC, /**< Fully uncached memory map */
    IRIS_MMAP_WC, /**< Write-combining map with no caching of reads */
    IRIS_MMAP_WB, /**< Write-back mapping with CPU caches enabled */

src/gallium/drivers/iris/iris_resource.c

@@ -2087,7 +2087,7 @@ iris_transfer_map(struct pipe_context *ctx,
    if (usage & PIPE_MAP_WRITE)
       util_range_add(&res->base.b, &res->valid_buffer_range, box->x, box->x + box->width);
 
-   if (!res->bo->imported) {
+   if (res->bo->mmap_mode != IRIS_MMAP_NONE) {
       /* GPU copies are not useful for buffer reads.  Instead of stalling to
        * read from the original buffer, we'd simply copy it to a temporary...
        * then stall (a bit longer) to read from that buffer.
@@ -2257,7 +2257,8 @@ iris_texture_subdata(struct pipe_context *ctx,
     */
    if (surf->tiling == ISL_TILING_LINEAR ||
        isl_aux_usage_has_compression(res->aux.usage) ||
-       resource_is_busy(ice, res)) {
+       resource_is_busy(ice, res) ||
+       res->bo->mmap_mode == IRIS_MMAP_NONE) {
       return u_default_texture_subdata(ctx, resource, level, usage, box,
                                        data, stride, layer_stride);
    }