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a=openpgp-sha256; l=4012; i=vishal.l.verma@intel.com; h=from:subject:message-id; bh=LlNwsQ9722KaImXgMJUAbGVELQS9Qj5zVBOISdpjDqE=; b=owGbwMvMwCXGf25diOft7jLG02pJDKkbc50VeD8v+CjLFhJhfFzu8RSjtH97erzz9l4Qf8Enc LfQ66hyRykLgxgXg6yYIsvfPR8Zj8ltz+cJTHCEmcPKBDKEgYtTACbiH8TwV1Ju2kePSfLnrhke 2viisS8mpjzc/qGgQObvl8E/GFTs9Rn+B7+fyvC/VG61dh1TyJMbdnVpnpttknc4N2ev5nkgpin HBAA= X-Developer-Key: i=vishal.l.verma@intel.com; a=openpgp; fpr=F8682BE134C67A12332A2ED07AFA61BEA3B84DFF X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: BE40440010 X-Stat-Signature: r1hiu5ahx99tft8p9j58pb3hgfm8bxen X-Rspam-User: X-HE-Tag: 1706126667-576059 X-HE-Meta: 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 k7bXDJL4 oJQismCpeIBTcvBRzDL6jdskJ6tNZo3rmkzUwyBGue4APZfvnzllqQKXY3eal3v/sD0No2LjX/DOyG/CiNmrAskhoiuI2H8Hl6gPvJfInj6lfMNOmwV0KQFUZpndjhp7vo2FgPZcuGlvWWMQB7g2+npGv32BTchn8DSsfX23nIAC53y6HLsYUd6YxsG+kVEYs9qh54dtkaEB+31rJHY650cXS6arXGs1VGFc5wvjVfxmkvOMU3eB0C8qoM0MXbMajECXBIujeAmYBaGz7ofZ784htm2n62/bWcsEuArqlCDZT+3EmptznRAqYhg== 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: 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 Reviewed-by: Huang, Ying Signed-off-by: Vishal Verma Reviewed-by: Alison Schofield --- 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'."