}
EXPORT_SYMBOL_NS_GPL(cxl_dpa_debug, "CXL");
+/* See request_skip() kernel-doc */
+static resource_size_t __adjust_skip(struct cxl_dev_state *cxlds,
+ const resource_size_t skip_base,
+ const resource_size_t skip_len,
+ const char *requester)
+{
+ const resource_size_t skip_end = skip_base + skip_len - 1;
+
+ for (int i = 0; i < cxlds->nr_partitions; i++) {
+ const struct resource *part_res = &cxlds->part[i].res;
+ resource_size_t adjust_start, adjust_end, size;
+
+ adjust_start = max(skip_base, part_res->start);
+ adjust_end = min(skip_end, part_res->end);
+
+ if (adjust_end < adjust_start)
+ continue;
+
+ size = adjust_end - adjust_start + 1;
+
+ if (!requester)
+ __release_region(&cxlds->dpa_res, adjust_start, size);
+ else if (!__request_region(&cxlds->dpa_res, adjust_start, size,
+ requester, 0))
+ return adjust_start - skip_base;
+ }
+
+ return skip_len;
+}
+#define release_skip(c, b, l) __adjust_skip((c), (b), (l), NULL)
+
/*
* Must be called in a context that synchronizes against this decoder's
* port ->remove() callback (like an endpoint decoder sysfs attribute)
skip_start = res->start - cxled->skip;
__release_region(&cxlds->dpa_res, res->start, resource_size(res));
if (cxled->skip)
- __release_region(&cxlds->dpa_res, skip_start, cxled->skip);
+ release_skip(cxlds, skip_start, cxled->skip);
cxled->skip = 0;
cxled->dpa_res = NULL;
put_device(&cxled->cxld.dev);
__cxl_dpa_release(cxled);
}
+/**
+ * request_skip() - Track DPA 'skip' in @cxlds->dpa_res resource tree
+ * @cxlds: CXL.mem device context that parents @cxled
+ * @cxled: Endpoint decoder establishing new allocation that skips lower DPA
+ * @skip_base: DPA < start of new DPA allocation (DPAnew)
+ * @skip_len: @skip_base + @skip_len == DPAnew
+ *
+ * DPA 'skip' arises from out-of-sequence DPA allocation events relative
+ * to free capacity across multiple partitions. It is a wasteful event
+ * as usable DPA gets thrown away, but if a deployment has, for example,
+ * a dual RAM+PMEM device, wants to use PMEM, and has unallocated RAM
+ * DPA, the free RAM DPA must be sacrificed to start allocating PMEM.
+ * See third "Implementation Note" in CXL 3.1 8.2.4.19.13 "Decoder
+ * Protection" for more details.
+ *
+ * A 'skip' always covers the last allocated DPA in a previous partition
+ * to the start of the current partition to allocate. Allocations never
+ * start in the middle of a partition, and allocations are always
+ * de-allocated in reverse order (see cxl_dpa_free(), or natural devm
+ * unwind order from forced in-order allocation).
+ *
+ * If @cxlds->nr_partitions was guaranteed to be <= 2 then the 'skip'
+ * would always be contained to a single partition. Given
+ * @cxlds->nr_partitions may be > 2 it results in cases where the 'skip'
+ * might span "tail capacity of partition[0], all of partition[1], ...,
+ * all of partition[N-1]" to support allocating from partition[N]. That
+ * in turn interacts with the partition 'struct resource' boundaries
+ * within @cxlds->dpa_res whereby 'skip' requests need to be divided by
+ * partition. I.e. this is a quirk of using a 'struct resource' tree to
+ * detect range conflicts while also tracking partition boundaries in
+ * @cxlds->dpa_res.
+ */
+static int request_skip(struct cxl_dev_state *cxlds,
+ struct cxl_endpoint_decoder *cxled,
+ const resource_size_t skip_base,
+ const resource_size_t skip_len)
+{
+ resource_size_t skipped = __adjust_skip(cxlds, skip_base, skip_len,
+ dev_name(&cxled->cxld.dev));
+
+ if (skipped == skip_len)
+ return 0;
+
+ dev_dbg(cxlds->dev,
+ "%s: failed to reserve skipped space (%pa %pa %pa)\n",
+ dev_name(&cxled->cxld.dev), &skip_base, &skip_len, &skipped);
+
+ release_skip(cxlds, skip_base, skipped);
+
+ return -EBUSY;
+}
+
static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
resource_size_t base, resource_size_t len,
resource_size_t skipped)
struct cxl_port *port = cxled_to_port(cxled);
struct cxl_dev_state *cxlds = cxlmd->cxlds;
struct device *dev = &port->dev;
+ enum cxl_decoder_mode mode;
struct resource *res;
+ int rc;
lockdep_assert_held_write(&cxl_dpa_rwsem);
}
if (skipped) {
- res = __request_region(&cxlds->dpa_res, base - skipped, skipped,
- dev_name(&cxled->cxld.dev), 0);
- if (!res) {
- dev_dbg(dev,
- "decoder%d.%d: failed to reserve skipped space\n",
- port->id, cxled->cxld.id);
- return -EBUSY;
- }
+ rc = request_skip(cxlds, cxled, base - skipped, skipped);
+ if (rc)
+ return rc;
}
res = __request_region(&cxlds->dpa_res, base, len,
dev_name(&cxled->cxld.dev), 0);
dev_dbg(dev, "decoder%d.%d: failed to reserve allocation\n",
port->id, cxled->cxld.id);
if (skipped)
- __release_region(&cxlds->dpa_res, base - skipped,
- skipped);
+ release_skip(cxlds, base - skipped, skipped);
return -EBUSY;
}
cxled->dpa_res = res;
cxled->skip = skipped;
- if (to_pmem_res(cxlds) && resource_contains(to_pmem_res(cxlds), res))
- cxled->mode = CXL_DECODER_PMEM;
- else if (to_ram_res(cxlds) && resource_contains(to_ram_res(cxlds), res))
- cxled->mode = CXL_DECODER_RAM;
- else {
+ mode = CXL_DECODER_NONE;
+ for (int i = 0; cxlds->nr_partitions; i++)
+ if (resource_contains(&cxlds->part[i].res, res)) {
+ mode = cxl_part_mode(cxlds->part[i].mode);
+ break;
+ }
+
+ if (mode == CXL_DECODER_NONE)
dev_warn(dev, "decoder%d.%d: %pr does not map any partition\n",
port->id, cxled->cxld.id, res);
- cxled->mode = CXL_DECODER_NONE;
- }
+ cxled->mode = mode;
port->hdm_end++;
get_device(&cxled->cxld.dev);
int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
{
struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
- resource_size_t free_ram_start, free_pmem_start;
struct cxl_port *port = cxled_to_port(cxled);
struct cxl_dev_state *cxlds = cxlmd->cxlds;
struct device *dev = &cxled->cxld.dev;
- resource_size_t start, avail, skip;
+ struct resource *res, *prev = NULL;
+ resource_size_t start, avail, skip, skip_start;
struct resource *p, *last;
- const struct resource *ram_res = to_ram_res(cxlds);
- const struct resource *pmem_res = to_pmem_res(cxlds);
- int rc;
+ int part, rc;
down_write(&cxl_dpa_rwsem);
if (cxled->cxld.region) {
goto out;
}
- for (p = ram_res->child, last = NULL; p; p = p->sibling)
- last = p;
- if (last)
- free_ram_start = last->end + 1;
- else
- free_ram_start = ram_res->start;
+ part = -1;
+ for (int i = 0; i < cxlds->nr_partitions; i++) {
+ if (cxled->mode == cxl_part_mode(cxlds->part[i].mode)) {
+ part = i;
+ break;
+ }
+ }
+
+ if (part < 0) {
+ rc = -EBUSY;
+ goto out;
+ }
- for (p = pmem_res->child, last = NULL; p; p = p->sibling)
+ res = &cxlds->part[part].res;
+ for (p = res->child, last = NULL; p; p = p->sibling)
last = p;
if (last)
- free_pmem_start = last->end + 1;
+ start = last->end + 1;
else
- free_pmem_start = pmem_res->start;
+ start = res->start;
- if (cxled->mode == CXL_DECODER_RAM) {
- start = free_ram_start;
- avail = ram_res->end - start + 1;
- skip = 0;
- } else if (cxled->mode == CXL_DECODER_PMEM) {
- resource_size_t skip_start, skip_end;
-
- start = free_pmem_start;
- avail = pmem_res->end - start + 1;
- skip_start = free_ram_start;
-
- /*
- * If some pmem is already allocated, then that allocation
- * already handled the skip.
- */
- if (pmem_res->child &&
- skip_start == pmem_res->child->start)
- skip_end = skip_start - 1;
- else
- skip_end = start - 1;
- skip = skip_end - skip_start + 1;
- } else {
- dev_dbg(dev, "mode not set\n");
- rc = -EINVAL;
- goto out;
+ /*
+ * To allocate at partition N, a skip needs to be calculated for all
+ * unallocated space at lower partitions indices.
+ *
+ * If a partition has any allocations, the search can end because a
+ * previous cxl_dpa_alloc() invocation is assumed to have accounted for
+ * all previous partitions.
+ */
+ skip_start = CXL_RESOURCE_NONE;
+ for (int i = part; i; i--) {
+ prev = &cxlds->part[i - 1].res;
+ for (p = prev->child, last = NULL; p; p = p->sibling)
+ last = p;
+ if (last) {
+ skip_start = last->end + 1;
+ break;
+ }
+ skip_start = prev->start;
}
+ avail = res->end - start + 1;
+ if (skip_start == CXL_RESOURCE_NONE)
+ skip = 0;
+ else
+ skip = res->start - skip_start;
+
if (size > avail) {
dev_dbg(dev, "%pa exceeds available %s capacity: %pa\n", &size,
cxl_decoder_mode_name(cxled->mode), &avail);
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