From: "Huang, Ying" <ying.huang@intel.com>
To: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
<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>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
<linux-mm@kvack.org>, "Li Zhijian" <lizhijian@fujitsu.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: Re: [PATCH v5 4/4] dax: add a sysfs knob to control memmap_on_memory behavior
Date: Fri, 15 Dec 2023 12:53:40 +0800 [thread overview]
Message-ID: <87h6kkqd63.fsf@yhuang6-desk2.ccr.corp.intel.com> (raw)
In-Reply-To: <20231214-vv-dax_abi-v5-4-3f7b006960b4@intel.com> (Vishal Verma's message of "Thu, 14 Dec 2023 00:37:57 -0700")
Vishal Verma <vishal.l.verma@intel.com> writes:
> 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>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
> drivers/dax/bus.c | 38 +++++++++++++++++++++++++++++++++
> Documentation/ABI/testing/sysfs-bus-dax | 17 +++++++++++++++
> 2 files changed, 55 insertions(+)
>
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index 6226de131d17..f4d3beec507c 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -1245,6 +1245,43 @@ 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 sprintf(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);
> + struct dax_device_driver *dax_drv;
> + ssize_t rc;
> + bool val;
> +
> + 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;
> + }
> +
> + guard(device)(dev);
> + dax_drv = to_dax_drv(dev->driver);
Although "struct driver" is the first member of "struct
dax_device_driver", I feel the code is fragile to depends on that. Can
we check dev->driver directly instead?
--
Best Regards,
Huang, Ying
> + if (dax_drv && dev_dax->memmap_on_memory != val &&
> + dax_drv->type == DAXDRV_KMEM_TYPE)
> + return -EBUSY;
> + dev_dax->memmap_on_memory = val;
> +
> + 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);
> @@ -1271,6 +1308,7 @@ 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..40d9965733b2 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: October, 2023
> +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'."
prev parent reply other threads:[~2023-12-15 4:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-14 7:37 [PATCH v5 0/4] Add DAX ABI for memmap_on_memory Vishal Verma
2023-12-14 7:37 ` [PATCH v5 1/4] Documentatiion/ABI: Add ABI documentation for sys-bus-dax Vishal Verma
2023-12-14 7:37 ` [PATCH v5 2/4] dax/bus: Use guard(device) in sysfs attribute helpers Vishal Verma
2023-12-14 7:37 ` [PATCH v5 3/4] mm/memory_hotplug: export mhp_supports_memmap_on_memory() Vishal Verma
2023-12-14 9:10 ` David Hildenbrand
2023-12-14 7:37 ` [PATCH v5 4/4] dax: add a sysfs knob to control memmap_on_memory behavior Vishal Verma
2023-12-14 8:31 ` Greg Kroah-Hartman
2023-12-15 4:53 ` Huang, Ying [this message]
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