Export qtg_id sysfs attributes for the CXL memory device. The QTG ID should show up as /sys/bus/cxl/devices/memX/qtg_id. The QTG ID is retrieved via _DSM after supplying the caluclated bandwidth and latency for the entire CXL path from device to the CPU. This ID is used to match up to the root decoder QTG ID to determine which CFMWS the memory range of a hotplugged CXL mem device should be assigned under. While there may be multiple DSMAS exported by the device CDAT, the driver will only expose the first QTG ID in sysfs for now. In the future when multiple QTG IDs are necessary, they can be exposed. [1] [1]: https://lore.kernel.org/linux-cxl/167571650007.587790.10040913293130712882.stgit@djiang5-mobl3.local/T/#md2a47b1ead3e1ba08f50eab29a4af1aed1d215ab Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx> Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx> --- Documentation/ABI/testing/sysfs-bus-cxl | 11 +++++++++++ drivers/cxl/core/memdev.c | 15 +++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl index 471ac9a37078..a018f0a21aca 100644 --- a/Documentation/ABI/testing/sysfs-bus-cxl +++ b/Documentation/ABI/testing/sysfs-bus-cxl @@ -58,6 +58,17 @@ Description: affinity for this device. +What: /sys/bus/cxl/devices/memX/qtg_id +Date: March, 2024 +KernelVersion: v6.4 +Contact: linux-cxl@xxxxxxxxxxxxxxx +Description: + (RO) Show the first QoS Throttling Group ID for the device. + The ID is used to match against the CFMWS (root decoder) + QTG ID so that the memory range under a hot-plugged device + is assigned under the appropriate CFMWS. + + What: /sys/bus/cxl/devices/*/devtype Date: June, 2021 KernelVersion: v5.14 diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c index d2605fc39240..974eff833edd 100644 --- a/drivers/cxl/core/memdev.c +++ b/drivers/cxl/core/memdev.c @@ -106,12 +106,27 @@ static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR_RO(numa_node); +static ssize_t qtg_id_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct cxl_memdev *cxlmd = to_cxl_memdev(dev); + struct qos_prop_entry *qos; + + if (list_empty(&cxlmd->qos_list)) + return 0; + + qos = list_first_entry(&cxlmd->qos_list, struct qos_prop_entry, list); + return sysfs_emit(buf, "%u\n", qos->qtg_id); +} +static DEVICE_ATTR_RO(qtg_id); + static struct attribute *cxl_memdev_attributes[] = { &dev_attr_serial.attr, &dev_attr_firmware_version.attr, &dev_attr_payload_max.attr, &dev_attr_label_storage_size.attr, &dev_attr_numa_node.attr, + &dev_attr_qtg_id.attr, NULL, };
