From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26B8BC4332F for ; Tue, 12 Dec 2023 00:32:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345476AbjLLAcb (ORCPT ); Mon, 11 Dec 2023 19:32:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345592AbjLLAcZ (ORCPT ); Mon, 11 Dec 2023 19:32:25 -0500 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20A62114; Mon, 11 Dec 2023 16:32:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1702341149; x=1733877149; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=sPE11n3k/pEWxftH1qy2EYfcLYrjmwVTl6Ayyfeju2w=; b=MUlzn2wyWEQrHN14U9f4lwUBuxDMaL1aQod5Tu8xr0jWp6mlgE1Yg1Rf hSrbaKVRKcCDmnqZ2bPPnRH78O0WVRJiMR2g0srUMAAUgCQ40QEBapL6U b5bZXKKGXw2Ax+kdxnN9Kn07Scyzw+z0k2hVZY5hP9OomiVMt1GUPyodm gtdT2kVeeJLO3V7m0nnYSG6gNcas5cEHyqA2Wrl4AJd3Zh9pdg+LeFvQW cAhxMKEFbkxd9FJEq/YPINW98lWLJJF1IbIF1Wie8kICUf9QSWtvbeRsy cSKlZxa1Rf+qJ3HsGHkFoez5/bPt5Hzi9QzpHwrLG+boJ41HGNRR2aqF2 w==; X-IronPort-AV: E=McAfee;i="6600,9927,10921"; a="393605446" X-IronPort-AV: E=Sophos;i="6.04,269,1695711600"; d="scan'208";a="393605446" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Dec 2023 16:32:28 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10921"; a="1020466528" X-IronPort-AV: E=Sophos;i="6.04,269,1695711600"; d="scan'208";a="1020466528" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Dec 2023 16:32:25 -0800 From: "Huang, Ying" To: Vishal Verma Cc: Dan Williams , Dave Jiang , , , , David Hildenbrand , "Dave Hansen" , "Li Zhijian" , Jonathan Cameron Subject: Re: [PATCH v3 2/2] dax: add a sysfs knob to control memmap_on_memory behavior In-Reply-To: <20231211-vv-dax_abi-v3-2-acf6cc1bde9f@intel.com> (Vishal Verma's message of "Mon, 11 Dec 2023 15:52:18 -0700") References: <20231211-vv-dax_abi-v3-0-acf6cc1bde9f@intel.com> <20231211-vv-dax_abi-v3-2-acf6cc1bde9f@intel.com> Date: Tue, 12 Dec 2023 08:30:26 +0800 Message-ID: <87msugxnx9.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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > drivers/dax/bus.c | 47 +++++++++++++++++++++++++++++++++ > Documentation/ABI/testing/sysfs-bus-dax | 17 ++++++++++++ > 2 files changed, 64 insertions(+) > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index 1ff1ab5fa105..2871e5188f0d 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -1270,6 +1270,52 @@ 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 device_driver *drv = dev->driver; > + struct dev_dax *dev_dax = to_dev_dax(dev); > + struct dax_region *dax_region = dev_dax->region; > + struct dax_device_driver *dax_drv = to_dax_drv(drv); > + ssize_t rc; > + bool val; > + > + rc = kstrtobool(buf, &val); > + if (rc) > + return rc; > + > + if (dev_dax->memmap_on_memory == val) > + return len; > + > + device_lock(dax_region->dev); > + if (!dax_region->dev->driver) { > + device_unlock(dax_region->dev); > + return -ENXIO; > + } I think that it should be OK to write to "memmap_on_memory" if no driver is bound to the device. We just need to avoid to write to it when kmem driver is bound. -- Best Regards, Huang, Ying > + > + if (dax_drv->type == DAXDRV_KMEM_TYPE) { > + device_unlock(dax_region->dev); > + return -EBUSY; > + } > + > + device_lock(dev); > + dev_dax->memmap_on_memory = val; > + device_unlock(dev); > + > + device_unlock(dax_region->dev); > + 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); > @@ -1296,6 +1342,7 @@ 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 a61a7b186017..b1fd8bf8a7de 100644 > --- a/Documentation/ABI/testing/sysfs-bus-dax > +++ b/Documentation/ABI/testing/sysfs-bus-dax > @@ -149,3 +149,20 @@ 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'."