Re: [PATCH 1/6] drm/i915/ttm: add ttm_buddy_man

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On 6/8/21 10:11 AM, Matthew Auld wrote:
On 08/06/2021 08:11, Thomas Hellström wrote:
On Mon, 2021-06-07 at 19:22 +0100, Matthew Auld wrote:
Add back our standalone i915_buddy allocator and integrate it into a
ttm_resource_manager. This will plug into our ttm backend for
managing
device local-memory in the next couple of patches.

Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---


Since the buddy + selftests have been part of the driver before, I
didn't review them separately, but for the TTM interface, some minor
comments below. With those fixed,

Acked-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>


diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
new file mode 100644
index 000000000000..d7bf37be1932
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+
+#include <linux/slab.h>
+
+#include <drm/ttm/ttm_bo_driver.h>
+#include <drm/ttm/ttm_placement.h>
+
+#include "i915_ttm_buddy_manager.h"
+
+#include "i915_buddy.h"
+#include "i915_gem.h"
+
+struct i915_ttm_buddy_manager {
+       struct ttm_resource_manager manager;
+       struct i915_buddy_mm mm;
+       struct list_head reserved;
+       struct mutex lock;
+};
+
+static inline struct i915_ttm_buddy_manager *

"inline" shouldn't be needed here.

+to_buddy_manager(struct ttm_resource_manager *man)
+{
+       return container_of(man, struct i915_ttm_buddy_manager,
manager);
+}
+
+static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager
*man,
+                                   struct ttm_buffer_object *bo,
+                                   const struct ttm_place *place,
+                                   struct ttm_resource **res)
+{
+       struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
+       struct i915_ttm_buddy_resource *bman_res;
+       struct i915_buddy_mm *mm = &bman->mm;
+       unsigned long n_pages;
+       unsigned int min_order;
+       u64 size;
+       int err;
+
+       GEM_BUG_ON(place->fpfn || place->lpfn);
+       GEM_BUG_ON(bo->page_alignment < mm->chunk_size);
+
+       bman_res = kzalloc(sizeof(*bman_res), GFP_KERNEL);
+       if (!bman_res)
+               return -ENOMEM;
+
+       ttm_resource_init(bo, place, &bman_res->base);
+       INIT_LIST_HEAD(&bman_res->blocks);
+       bman_res->mm = mm;
+
+       GEM_BUG_ON(!bman_res->base.num_pages);
+       size = bman_res->base.num_pages << PAGE_SHIFT;
+
+       min_order = ilog2(bo->page_alignment) - ilog2(mm-
chunk_size);
+       if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
+               size = roundup_pow_of_two(size);
+               min_order = ilog2(size) - ilog2(mm->chunk_size);
+       }
+
+       if (size > mm->size) {
+               err = -E2BIG;
+               goto err_free_res;
+       }
+
+       n_pages = size >> ilog2(mm->chunk_size);
+
+       do {
+               struct i915_buddy_block *block;
+               unsigned int order;
+
+               order = fls(n_pages) - 1;
+               GEM_BUG_ON(order > mm->max_order);
+               GEM_BUG_ON(order < min_order);
+
+               do {
+                       mutex_lock(&bman->lock);
+                       block = i915_buddy_alloc(mm, order);
+                       mutex_unlock(&bman->lock);
+                       if (!IS_ERR(block))
+                               break;
+
+                       if (order-- == min_order) {
+                               err = -ENXIO;

IIRC, TTM relies on -ENOSPC to retry with evictions.

Ah, right. We convert that back to -ENXIO in the upper levels somewhere?

Yes, that's done in the ttm bo backend after ttm_bo_validate() and bo initialization.

/Thomas


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