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X-IronPort-AV: E=McAfee;i="6600,9927,10924"; a="8587935" X-IronPort-AV: E=Sophos;i="6.04,277,1695711600"; d="scan'208";a="8587935" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Dec 2023 20:55:44 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.04,277,1695711600"; d="scan'208";a="22699992" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Dec 2023 20:55:40 -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 v5 4/4] dax: add a sysfs knob to control memmap_on_memory behavior 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") References: <20231214-vv-dax_abi-v5-0-3f7b006960b4@intel.com> <20231214-vv-dax_abi-v5-4-3f7b006960b4@intel.com> Date: Fri, 15 Dec 2023 12:53:40 +0800 Message-ID: <87h6kkqd63.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: 2593E140004 X-Rspam-User: X-Stat-Signature: e33w9ke7r47z44zb7x983swjwq37yxx7 X-Rspamd-Server: rspam01 X-HE-Tag: 1702616144-729192 X-HE-Meta: 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 4+ChDvNR kJeMMl0x4N2Jj2pJysvoCJWtvO/YBmC1pkg61JOPoj41T/HZV45MC3kflvOwyf6vmUrlmKPkFdP3pQNP6h2MTnYU1RvzVgP4GNHgtEepOlG6wQTHP96V2WidacnFJyNgULus+qlN/G6q+1tZzM9m1XAcIyg1pbcxJrftmKZBSFgfl15IJ68ZojXsxg26Dla4/OfK7CIjwLs7sAbUkh6V1uR3kFTnDFbFF//V66nPj9IdlmZAtJPaTmxxm0DT+7ucmtQIWo2VfvpRX2dPVTQ4o7kU0QZPaSYpbYbBlAuwRwfK6Bp0C/Vwf4NkOcNR4FQ02CemG 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 > --- > 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'."