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cxl/region: Add a region sysfs interface for region lock status

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There are 3 scenarios that leads to a locked region:
1. A region is created on a root decoder with Fixed Device Confiuration
   attribute.
2. CXL_HDM_DECODER0_CTRL_LOCK.

Both 1 & 1 are well described in:
commit 2230c4bdc4 ("cxl: Add handling of locked CXL decoder")

3) Platform that has region creation with PRMT address translation always
   locks the region, regardless of the FIXED attribute or decoder ctrl bit.

Region locked means region destroy operations are not permitted. CXL
region driver returns -EPERM for region destroy operations.

Although the locked status of the corresponding root decoder implies the
region is also locked, exposing the region lock status directly to
userspace improves usability for users who may not be aware of this
relationship.

[ dj: Amended commit log with additional locking scenarios. ]

Signed-off-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alejandro Lucero <alucerop@amd.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260401124951.1290041-1-ming.li@zohomail.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
This commit is contained in:
Li Ming
2026-04-01 20:49:51 +08:00
committed by Dave Jiang
parent 261a02b93d
commit d585bc86fb
2 changed files with 30 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
Documentation/ABI/testing/sysfs-bus-cxl
View File

@@ -508,6 +508,19 @@ Description:
(RO) The size of extended linear cache, if there is an extended
linear cache. Otherwise the attribute will not be visible.
What: /sys/bus/cxl/devices/regionZ/locked
Date: Mar, 2026
KernelVersion: v7.1
Contact: linux-cxl@vger.kernel.org
Description:
(RO) The CXL driver has the capability to lock a region based on
a BIOS or platform dependent configuration. Regions created as
locked are never permitted to be destroyed. Resets to participating
decoders will not result in a region destroy and will not free the
decoder resources.
What: /sys/bus/cxl/devices/regionZ/mode
Date: January, 2023
KernelVersion: v6.3

17
drivers/cxl/core/region.c
View File

@@ -767,6 +767,22 @@ static ssize_t extended_linear_cache_size_show(struct device *dev,
}
static DEVICE_ATTR_RO(extended_linear_cache_size);
static ssize_t locked_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct cxl_region *cxlr = to_cxl_region(dev);
int rc;
ACQUIRE(rwsem_read_intr, rwsem)(&cxl_rwsem.region);
if ((rc = ACQUIRE_ERR(rwsem_read_intr, &rwsem)))
return rc;
rc = test_bit(CXL_REGION_F_LOCK, &cxlr->flags);
return sysfs_emit(buf, "%d\n", rc);
}
static DEVICE_ATTR_RO(locked);
static struct attribute *cxl_region_attrs[] = {
&dev_attr_uuid.attr,
&dev_attr_commit.attr,
@@ -776,6 +792,7 @@ static struct attribute *cxl_region_attrs[] = {
&dev_attr_size.attr,
&dev_attr_mode.attr,
&dev_attr_extended_linear_cache_size.attr,
&dev_attr_locked.attr,
NULL,
};