* [PATCH 1/2] cxl/region: Try to add a region resource to a soft reserved parent
2023-06-24 1:24 [PATCH 0/2] cxl/region: Improve Soft Reserved resource handling alison.schofield
@ 2023-06-24 1:24 ` alison.schofield
2023-06-24 1:24 ` [PATCH 2/2] cxl/region: Remove a soft reserved resource at region teardown alison.schofield
1 sibling, 0 replies; 3+ messages in thread
From: alison.schofield @ 2023-06-24 1:24 UTC (permalink / raw)
To: Dan Williams, Ira Weiny, Vishal Verma, Dave Jiang, Ben Widawsky
Cc: Alison Schofield, linux-cxl
From: Alison Schofield <alison.schofield@intel.com>
During region autodiscovery, the region driver always inserts the
region resource as a child of the root decoder, a CXL WINDOW. It
has the effect of making a soft reserved resource, with an exactly
matching address range, a child of the region resource.
It looks like this in /proc/iomem:
2080000000-29dbfffffff : CXL Window 0
2080000000-247fffffff : region0
2080000000-247fffffff : Soft Reserved
Search for soft reserved resources that include the region resource,
and add the new region resource as a child of that found resource.
If a soft reserved resource is not found, insert to the root decoder
as usual.
With this change, it looks like this:
2080000000-29dbfffffff : CXL Window 0
2080000000-247fffffff : Soft Reserved
2080000000-247fffffff : region0
This odd parenting only occurs when the resources are an exact match.
When the region resource only uses part of a soft reserved resource,
the parenting appears more logical like this:
2080000000-29dbfffffff : CXL Window 0
2080000000-287fffffff : Soft Reserved
2080000000-247fffffff : region0
Aside from the more logical appearance, this change is in preparation
for further cleanup in region teardown. A follow-on patch intends to
find and free soft reserved resources upon region teardown.
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
drivers/cxl/core/region.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index f822de44bee0..1769ea92bf3a 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2652,6 +2652,28 @@ static int match_region_by_range(struct device *dev, void *data)
return rc;
}
+static int insert_resource_soft_reserved(struct resource *soft_res, void *arg)
+{
+ struct resource *parent, *new, *res = arg;
+ bool found = false;
+
+ parent = soft_res->parent;
+ if (!parent)
+ return 0;
+
+ /* Caller provides a copy of soft_res. Find the actual resource. */
+ for (new = parent->child; new; new = new->sibling) {
+ if (resource_contains(new, soft_res)) {
+ found = true;
+ break;
+ }
+ }
+ if (found)
+ return insert_resource(new, res) == 0;
+
+ return 0;
+}
+
/* Establish an empty region covering the given HPA range */
static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
struct cxl_endpoint_decoder *cxled)
@@ -2662,7 +2684,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
struct cxl_region_params *p;
struct cxl_region *cxlr;
struct resource *res;
- int rc;
+ int rc = 0;
do {
cxlr = __create_region(cxlrd, cxled->mode,
@@ -2698,7 +2720,13 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
dev_name(&cxlr->dev));
- rc = insert_resource(cxlrd->res, res);
+
+ /* Try inserting to a Soft Reserved parent, fallback to root decoder */
+ if (walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED, 0,
+ res->start, res->end, res,
+ insert_resource_soft_reserved) != 1)
+ rc = insert_resource(cxlrd->res, res);
+
if (rc) {
/*
* Platform-firmware may not have split resources like "System
--
2.37.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] cxl/region: Remove a soft reserved resource at region teardown
2023-06-24 1:24 [PATCH 0/2] cxl/region: Improve Soft Reserved resource handling alison.schofield
2023-06-24 1:24 ` [PATCH 1/2] cxl/region: Try to add a region resource to a soft reserved parent alison.schofield
@ 2023-06-24 1:24 ` alison.schofield
1 sibling, 0 replies; 3+ messages in thread
From: alison.schofield @ 2023-06-24 1:24 UTC (permalink / raw)
To: Dan Williams, Ira Weiny, Vishal Verma, Dave Jiang, Ben Widawsky
Cc: Alison Schofield, linux-cxl, Derick Marks
From: Alison Schofield <alison.schofield@intel.com>
When CXL regions are created through autodiscovery their resource
may be a child of a soft reserved resource. Today, when such a
region is destroyed, its soft reserved resource remains in place.
That means that the HPA range that the region could release, is
actually unavailable for reuse.
Free the soft reserved resource on region teardown by examining
the alignment of the resources, and handling accordingly. The
two resources, will be exactly aligned, partially aligned, or not
aligned at all.
|----------- "Soft Reserved" -----------|
|-------------- "Region #" -------------|
Exactly aligned. Any dangling children move up to a parent on removal.
The removal of this soft reserved seems guaranteed, however, the
availability of the address range for use depends on complete cleanup
of the region's child resources also.
|----------- "Soft Reserved" -----------|
|-------- "Region #" -------|
or
|----------- "Soft Reserved" -----------|
|-------- "Region #" -------|
Either start or end aligns. Unlike removing a resource, which simply
moves child resources up the resource tree, adjustments fail if any
child resources map the range being truncated. So, this one will fail
for dangling child resources of the region.
|---------- "Soft Reserved" ----------|
|---- "Region #" ----|
No alignment. Freeing the resource of a region in the middle is possible
if no child resources map the leading or trailing address space.
Reported-by: Derick Marks <derick.w.marks@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
drivers/cxl/core/region.c | 132 +++++++++++++++++++++++++++++++++++---
1 file changed, 123 insertions(+), 9 deletions(-)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 1769ea92bf3a..2cdb9a2770f3 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -525,22 +525,136 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
return 0;
}
+static int add_soft_reserved(struct resource *parent, resource_size_t start,
+ resource_size_t len, unsigned long flags)
+{
+ struct resource *res;
+ int rc;
+
+ res = kmalloc(sizeof(*res), GFP_KERNEL);
+ if (!res)
+ return -ENOMEM;
+
+ *res = DEFINE_RES_MEM_NAMED(start, len, "Soft Reserved");
+
+ res->desc = IORES_DESC_SOFT_RESERVED;
+ res->flags = res->flags | flags;
+ rc = insert_resource(parent, res);
+ if (rc)
+ kfree(res);
+
+ return rc;
+}
+
+static void remove_soft_reserved(struct cxl_region *cxlr, struct resource *soft,
+ resource_size_t start, resource_size_t end)
+{
+ struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+ resource_size_t new_start, new_end;
+ struct resource *parent;
+ unsigned long flags;
+ int rc;
+
+ /* Prevent new usage while removing or adjusting the resource */
+ mutex_lock(&cxlrd->range_lock);
+
+ /* Aligns at both resource start and end */
+ if (soft->start == start && soft->end == end) {
+ rc = remove_resource(soft);
+ if (rc)
+ dev_dbg(&cxlr->dev,
+ "cannot remove soft reserved resource %pr\n",
+ soft);
+ else
+ kfree(soft);
+
+ goto out;
+ }
+
+ /* Aligns at either resource start or end */
+ if (soft->start == start || soft->end == end) {
+ if (soft->start == start) {
+ new_start = end + 1;
+ new_end = soft->end;
+ } else {
+ new_start = soft->start;
+ new_end = start + 1;
+ }
+ rc = adjust_resource(soft, new_start, new_end - new_start + 1);
+ if (rc)
+ dev_dbg(&cxlr->dev,
+ "cannot adjust soft reserved resource %pr\n",
+ soft);
+ goto out;
+ }
+
+ /*
+ * No alignment. Attempt a 3-way split that removes the part of
+ * the resource the region occupied, and then creates new soft
+ * reserved resources for the leading and trailing addr space.
+ * adjust_resource() will stop the attempt if there are any
+ * child resources.
+ */
+
+ /* Save the original soft reserved resource params before adjusting */
+ new_start = soft->start;
+ new_end = soft->end;
+ parent = soft->parent;
+ flags = soft->flags;
+
+ rc = adjust_resource(soft, start, end - start);
+ if (rc) {
+ dev_dbg(&cxlr->dev,
+ "cannot adjust soft reserved resource %pr\n", soft);
+ goto out;
+ }
+ rc = remove_resource(soft);
+ if (rc)
+ dev_warn(&cxlr->dev,
+ "cannot remove soft reserved resource %pr\n", soft);
+
+ rc = add_soft_reserved(parent, new_start, start - new_start, flags);
+ if (rc)
+ dev_warn(&cxlr->dev,
+ "cannot add new soft reserved resource at %pa\n",
+ &new_start);
+
+ rc = add_soft_reserved(parent, end + 1, new_end - end, flags);
+ if (rc)
+ dev_warn(&cxlr->dev,
+ "cannot add new soft reserved resource at %pa + 1\n",
+ &end);
+out:
+ mutex_unlock(&cxlrd->range_lock);
+}
+
static void cxl_region_iomem_release(struct cxl_region *cxlr)
{
struct cxl_region_params *p = &cxlr->params;
+ struct resource *parent, *res = p->res;
+ resource_size_t start, end;
if (device_is_registered(&cxlr->dev))
lockdep_assert_held_write(&cxl_region_rwsem);
- if (p->res) {
- /*
- * Autodiscovered regions may not have been able to insert their
- * resource.
- */
- if (p->res->parent)
- remove_resource(p->res);
- kfree(p->res);
- p->res = NULL;
+ if (!res)
+ return;
+ /*
+ * Autodiscovered regions may not have been able to insert their
+ * resource. If a Soft Reserved parent resource exists, try to
+ * remove that also.
+ */
+ if (p->res->parent) {
+ parent = p->res->parent;
+ start = p->res->start;
+ end = p->res->end;
+ remove_resource(p->res);
+ if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags) &&
+ parent->desc == IORES_DESC_SOFT_RESERVED)
+ remove_soft_reserved(cxlr, parent, start, end);
}
+
+ kfree(p->res);
+ p->res = NULL;
}
static int free_hpa(struct cxl_region *cxlr)
--
2.37.3
^ permalink raw reply related [flat|nested] 3+ messages in thread