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X-IronPort-AV: E=McAfee;i="6600,9927,10924"; a="461705871" X-IronPort-AV: E=Sophos;i="6.04,278,1695711600"; d="scan'208";a="461705871" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Dec 2023 23:55:12 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.04,278,1695711600"; d="scan'208";a="16200871" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orviesa002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Dec 2023 23:55:08 -0800 From: "Huang, Ying" To: Vishal Verma Cc: Dan Williams , Dave Jiang , Andrew Morton , Oscar Salvador , , , , David Hildenbrand , "Dave Hansen" , Greg Kroah-Hartman , , "Li Zhijian" , Jonathan Cameron Subject: Re: [PATCH v6 4/4] dax: add a sysfs knob to control memmap_on_memory behavior In-Reply-To: <20231214-vv-dax_abi-v6-4-ad900d698438@intel.com> (Vishal Verma's message of "Thu, 14 Dec 2023 22:25:29 -0700") References: <20231214-vv-dax_abi-v6-0-ad900d698438@intel.com> <20231214-vv-dax_abi-v6-4-ad900d698438@intel.com> Date: Fri, 15 Dec 2023 15:53:08 +0800 Message-ID: <871qbnrjff.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 52201C0007 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 1z8inrcepmwbxyh6jwhxq9zshqkiqjzc X-HE-Tag: 1702626913-775279 X-HE-Meta: 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 spAgSJVz aUguUxMLaQhn23QbGbFK/RFPEROnK/8ydx1FlwFIvkiMWgu4nKG03p2xKVCL7lw+Jgq0hHqtEVepIgAZz/zCq1Y/fpe5lWnYeE52OhMSAxlW9ju1NM2hQALgzL0TxrIO4AL3iBxQBlLEw8WicrsSiQLifsDYbqErtH5eWL8QvQS+6auNfk7iLofklRGErEaXtx2VbhO6anPToMDvkxnp0SXlWzAmb7hDenuhD0AHBdAMW7aBOo/NXOd6u6i+JaUlzlgBTF0uadaDTOVcSc3/lw7EPQzq1TsXU+SQMVn0Uhf5HQ7/tfolIsxQxU1MLgvkkO+Dy X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Vishal Verma 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 > Cc: Dan Williams > Cc: Dave Jiang > Cc: Dave Hansen > Cc: Huang Ying > Tested-by: Li Zhijian > Reviewed-by: Jonathan Cameron > Reviewed-by: David Hildenbrand > Signed-off-by: Vishal Verma Looks good to me! Thanks! Reviewed-by: "Huang, Ying" > --- > drivers/dax/bus.c | 36 +++++++++++++++++++++++++++++++++ > Documentation/ABI/testing/sysfs-bus-dax | 17 ++++++++++++++++ > 2 files changed, 53 insertions(+) > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index 6226de131d17..3622b3d1c0de 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -1245,6 +1245,41 @@ 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); > + 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); > + if (dev_dax->memmap_on_memory != val && dev->driver && > + to_dax_drv(dev->driver)->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 +1306,7 @@ 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'."