cxl: Add decoders_committed sysfs attribute to cxl_port

This attribute allows cxl-cli to determine whether there are decoders
committed to a memdev.  This is only a snapshot of the state, and
doesn't offer any protection or serialization against a concurrent
disable-region operation.

Reviewed-by: Jim Harris <jim.harris@samsung.com>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/169747907439.272156.10261062080830155662.stgit@djiang5-mobl3
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 087f762..432610f 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -178,6 +178,21 @@ Description:
                hardware decoder target list.
 
 
+What:          /sys/bus/cxl/devices/portX/decoders_committed
+Date:          October, 2023
+KernelVersion: v6.7
+Contact:       linux-cxl@vger.kernel.org
+Description:
+               (RO) A memory device is considered active when any of its
+               decoders are in the "committed" state (See CXL 3.0 8.2.4.19.7
+               CXL HDM Decoder n Control Register). Hotplug and destructive
+               operations like "sanitize" are blocked while device is actively
+               decoding a Host Physical Address range. Note that this number
+               may be elevated without any regionX objects active or even
+               enumerated, as this may be due to decoders established by
+               platform firwmare or a previous kernel (kexec).
+
+
 What:          /sys/bus/cxl/devices/decoderX.Y
 Date:          June, 2021
 KernelVersion: v5.14

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index d0ed98a..0adee1e 100644 (file)
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -534,8 +534,33 @@ static void cxl_port_release(struct device *dev)
        kfree(port);
 }
 
+static ssize_t decoders_committed_show(struct device *dev,
+                                      struct device_attribute *attr, char *buf)
+{
+       struct cxl_port *port = to_cxl_port(dev);
+       int rc;
+
+       down_read(&cxl_region_rwsem);
+       rc = sysfs_emit(buf, "%d\n", cxl_num_decoders_committed(port));
+       up_read(&cxl_region_rwsem);
+
+       return rc;
+}
+
+static DEVICE_ATTR_RO(decoders_committed);
+
+static struct attribute *cxl_port_attrs[] = {
+       &dev_attr_decoders_committed.attr,
+       NULL,
+};
+
+static struct attribute_group cxl_port_attribute_group = {
+       .attrs = cxl_port_attrs,
+};
+
 static const struct attribute_group *cxl_port_attribute_groups[] = {
        &cxl_base_attribute_group,
+       &cxl_port_attribute_group,
        NULL,
 };