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X-IronPort-AV: E=McAfee;i="6600,9927,10964"; a="466857917" X-IronPort-AV: E=Sophos;i="6.05,216,1701158400"; d="scan'208";a="466857917" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2024 13:40:28 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,216,1701158400"; d="scan'208";a="2787184" Received: from aschofie-mobl2.amr.corp.intel.com (HELO aschofie-mobl2) ([10.209.37.71]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2024 13:40:27 -0800 Date: Fri, 26 Jan 2024 13:40:25 -0800 From: Alison Schofield To: Vishal Verma Cc: Dan Williams , Dave Jiang , Andrew Morton , Oscar Salvador , linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, David Hildenbrand , Dave Hansen , Huang Ying , Greg Kroah-Hartman , Matthew Wilcox , linux-mm@kvack.org, Li Zhijian , Jonathan Cameron Subject: Re: [PATCH v7 5/5] dax: add a sysfs knob to control memmap_on_memory behavior Message-ID: References: <20240124-vv-dax_abi-v7-0-20d16cb8d23d@intel.com> <20240124-vv-dax_abi-v7-5-20d16cb8d23d@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240124-vv-dax_abi-v7-5-20d16cb8d23d@intel.com> X-Rspamd-Queue-Id: 03BE840011 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: rf86m9yq95kew7bxmranpiwctrd3q8hp X-HE-Tag: 1706305230-187664 X-HE-Meta: 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 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: On Wed, Jan 24, 2024 at 12:03:50PM -0800, Vishal Verma wrote: > 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. Reviewed-by: Alison Schofield > > 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 > Reviewed-by: Huang, Ying > Signed-off-by: Vishal Verma > --- > 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 > >