From: Vishal Verma <vishal.l.verma@intel.com>
To: Dan Williams <dan.j.williams@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>
Cc: linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev,
linux-cxl@vger.kernel.org, David Hildenbrand <david@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Huang Ying <ying.huang@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Matthew Wilcox <willy@infradead.org>,
linux-mm@kvack.org, Li Zhijian <lizhijian@fujitsu.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: [PATCH v7 5/5] dax: add a sysfs knob to control memmap_on_memory behavior
Date: Wed, 24 Jan 2024 12:03:50 -0800 [thread overview]
Message-ID: <20240124-vv-dax_abi-v7-5-20d16cb8d23d@intel.com> (raw)
In-Reply-To: <20240124-vv-dax_abi-v7-0-20d16cb8d23d@intel.com>
Add a sysfs knob for dax devices to control the memmap_on_memory setting
if the dax device were to be hotplugged as system memory.
The default memmap_on_memory setting for dax devices originating via
pmem or hmem is set to 'false' - i.e. no memmap_on_memory semantics, to
preserve legacy behavior. For dax devices via CXL, the default is on.
The sysfs control allows the administrator to override the above
defaults if needed.
Cc: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Tested-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Huang, Ying <ying.huang@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
drivers/dax/bus.c | 43 +++++++++++++++++++++++++++++++++
Documentation/ABI/testing/sysfs-bus-dax | 17 +++++++++++++
2 files changed, 60 insertions(+)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 0fd948a4443e..27c86d0ca711 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -1349,6 +1349,48 @@ static ssize_t numa_node_show(struct device *dev,
}
static DEVICE_ATTR_RO(numa_node);
+static ssize_t memmap_on_memory_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct dev_dax *dev_dax = to_dev_dax(dev);
+
+ return sysfs_emit(buf, "%d\n", dev_dax->memmap_on_memory);
+}
+
+static ssize_t memmap_on_memory_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct dev_dax *dev_dax = to_dev_dax(dev);
+ bool val;
+ int rc;
+
+ rc = kstrtobool(buf, &val);
+ if (rc)
+ return rc;
+
+ if (val == true && !mhp_supports_memmap_on_memory()) {
+ dev_dbg(dev, "memmap_on_memory is not available\n");
+ return -EOPNOTSUPP;
+ }
+
+ rc = down_write_killable(&dax_dev_rwsem);
+ if (rc)
+ return rc;
+
+ if (dev_dax->memmap_on_memory != val && dev->driver &&
+ to_dax_drv(dev->driver)->type == DAXDRV_KMEM_TYPE) {
+ up_write(&dax_dev_rwsem);
+ return -EBUSY;
+ }
+
+ dev_dax->memmap_on_memory = val;
+ up_write(&dax_dev_rwsem);
+
+ return len;
+}
+static DEVICE_ATTR_RW(memmap_on_memory);
+
static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int n)
{
struct device *dev = container_of(kobj, struct device, kobj);
@@ -1375,6 +1417,7 @@ static struct attribute *dev_dax_attributes[] = {
&dev_attr_align.attr,
&dev_attr_resource.attr,
&dev_attr_numa_node.attr,
+ &dev_attr_memmap_on_memory.attr,
NULL,
};
diff --git a/Documentation/ABI/testing/sysfs-bus-dax b/Documentation/ABI/testing/sysfs-bus-dax
index 6359f7bc9bf4..b34266bfae49 100644
--- a/Documentation/ABI/testing/sysfs-bus-dax
+++ b/Documentation/ABI/testing/sysfs-bus-dax
@@ -134,3 +134,20 @@ KernelVersion: v5.1
Contact: nvdimm@lists.linux.dev
Description:
(RO) The id attribute indicates the region id of a dax region.
+
+What: /sys/bus/dax/devices/daxX.Y/memmap_on_memory
+Date: January, 2024
+KernelVersion: v6.8
+Contact: nvdimm@lists.linux.dev
+Description:
+ (RW) Control the memmap_on_memory setting if the dax device
+ were to be hotplugged as system memory. This determines whether
+ the 'altmap' for the hotplugged memory will be placed on the
+ device being hotplugged (memmap_on_memory=1) or if it will be
+ placed on regular memory (memmap_on_memory=0). This attribute
+ must be set before the device is handed over to the 'kmem'
+ driver (i.e. hotplugged into system-ram). Additionally, this
+ depends on CONFIG_MHP_MEMMAP_ON_MEMORY, and a globally enabled
+ memmap_on_memory parameter for memory_hotplug. This is
+ typically set on the kernel command line -
+ memory_hotplug.memmap_on_memory set to 'true' or 'force'."
--
2.43.0
next prev parent reply other threads:[~2024-01-24 20:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 20:03 [PATCH v7 0/5] Add DAX ABI for memmap_on_memory Vishal Verma
2024-01-24 20:03 ` [PATCH v7 1/5] dax/bus.c: replace driver-core lock usage by a local rwsem Vishal Verma
2024-01-26 21:12 ` Alison Schofield
2024-03-12 20:07 ` Dan Williams
2024-03-12 20:20 ` Verma, Vishal L
2024-03-12 20:22 ` Andrew Morton
2024-01-24 20:03 ` [PATCH v7 2/5] dax/bus.c: replace several sprintf() with sysfs_emit() Vishal Verma
2024-01-26 21:14 ` Alison Schofield
2024-01-24 20:03 ` [PATCH v7 3/5] Documentatiion/ABI: Add ABI documentation for sys-bus-dax Vishal Verma
2024-01-24 20:03 ` [PATCH v7 4/5] mm/memory_hotplug: export mhp_supports_memmap_on_memory() Vishal Verma
2024-01-24 20:03 ` Vishal Verma [this message]
2024-01-26 21:40 ` [PATCH v7 5/5] dax: add a sysfs knob to control memmap_on_memory behavior Alison Schofield
2024-01-26 1:29 ` [PATCH v7 0/5] Add DAX ABI for memmap_on_memory Andrew Morton
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