| Message ID | 20231206-vv-dax_abi-v2-2-f4f4f2336d08@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add DAX ABI for memmap_on_memory | expand |
Hi Vishal, On 07/12/2023 12:36, Vishal Verma wrote: > + > +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 s/memmap_on+memory=1/memmap_on_memory=1 I have a question here What relationship about memmap_on_memory and 'ndctl-create-namespace -M' option which specifies where is the vmemmap backed memory. I'm confused that memmap_on_memory=1 and '-M dev' are the same for nvdimm devdax mode ? ndctl-create-namespace ... -M, --map= A pmem namespace in "fsdax" or "devdax" mode requires allocation of per-page metadata. The allocation can be drawn from either: • "mem": typical system memory • "dev": persistent memory reserved from the namespace :: Given relative capacities of "Persistent Memory" to "System RAM" the allocation defaults to reserving space out of the namespace directly ("--map=dev"). The overhead is 64-bytes per 4K (16GB per 1TB) on x86. Thanks Zhijian > + placed on regular memory (memmap_on_memory=0). This attribute > + must be set before the device is handed over to the 'kmem'
On Thu, 2023-12-07 at 08:29 +0000, Zhijian Li (Fujitsu) wrote: > Hi Vishal, > > > On 07/12/2023 12:36, Vishal Verma wrote: > > + > > +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 > > s/memmap_on+memory=1/memmap_on_memory=1 Thanks, will fix. > > > I have a question here > > What relationship about memmap_on_memory and 'ndctl-create-namespace > -M' option which > specifies where is the vmemmap backed memory. > I'm confused that memmap_on_memory=1 and '-M dev' are the same for > nvdimm devdax mode ? > The main difference is that memory that comes from non-nvdimm sources, such as hmem, or cxl, doesn't have a chance to set up the altmaps as pmem can with '-M dev'. For these, memmap_on_memory does this as part of the memory hotplug.
Vishal Verma <vishal.l.verma@intel.com> 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 <david@redhat.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Jiang <dave.jiang@intel.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Huang Ying <ying.huang@intel.com> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Reviewed-by: David Hildenbrand <david@redhat.com> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> > --- > drivers/dax/bus.c | 40 +++++++++++++++++++++++++++++++++ > Documentation/ABI/testing/sysfs-bus-dax | 13 +++++++++++ > 2 files changed, 53 insertions(+) > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index 1ff1ab5fa105..11abb57cc031 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -1270,6 +1270,45 @@ 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_region *dax_region = dev_dax->region; > + 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) { This still doesn't look right. Can we check whether the current driver is kmem? And only allow change if it's not kmem? -- Best Regards, Huang, Ying > + device_unlock(dax_region->dev); > + return -ENXIO; > + } > + > + device_lock(dev); > + dev_dax->memmap_on_memory = val; > + device_unlock(dev); > + > + device_unlock(dax_region->dev); > + return rc == 0 ? len : rc; > +} > +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 +1335,7 @@ 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..bb063a004e41 100644 > --- a/Documentation/ABI/testing/sysfs-bus-dax > +++ b/Documentation/ABI/testing/sysfs-bus-dax > @@ -149,3 +149,16 @@ 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).
On 08/12/2023 03:25, Verma, Vishal L wrote: > On Thu, 2023-12-07 at 08:29 +0000, Zhijian Li (Fujitsu) wrote: >> Hi Vishal, >> >> >> On 07/12/2023 12:36, Vishal Verma wrote: >>> + >>> +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 >> >> s/memmap_on+memory=1/memmap_on_memory=1 > > Thanks, will fix. >> >> >> I have a question here >> >> What relationship about memmap_on_memory and 'ndctl-create-namespace >> -M' option which >> specifies where is the vmemmap backed memory. >> I'm confused that memmap_on_memory=1 and '-M dev' are the same for >> nvdimm devdax mode ? >> > The main difference is that memory that comes from non-nvdimm sources, > such as hmem, or cxl, doesn't have a chance to set up the altmaps as > pmem can with '-M dev'. For these, memmap_on_memory does this as part > of the memory hotplug. Thanks for your explanation. (I wrongly thought nvdimm.kmem was also controlled by '-M dev' before) feel free add: Tested-by: Li Zhijian <lizhijian@fujitsu.com>
On 07.12.23 05:36, 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. > > Cc: David Hildenbrand <david@redhat.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Jiang <dave.jiang@intel.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Huang Ying <ying.huang@intel.com> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Reviewed-by: David Hildenbrand <david@redhat.com> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> > --- > drivers/dax/bus.c | 40 +++++++++++++++++++++++++++++++++ > Documentation/ABI/testing/sysfs-bus-dax | 13 +++++++++++ > 2 files changed, 53 insertions(+) > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index 1ff1ab5fa105..11abb57cc031 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -1270,6 +1270,45 @@ 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_region *dax_region = dev_dax->region; > + 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; > + } > + > + device_lock(dev); > + dev_dax->memmap_on_memory = val; > + device_unlock(dev); > + > + device_unlock(dax_region->dev); > + return rc == 0 ? len : rc; > +} > +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 +1335,7 @@ 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..bb063a004e41 100644 > --- a/Documentation/ABI/testing/sysfs-bus-dax > +++ b/Documentation/ABI/testing/sysfs-bus-dax > @@ -149,3 +149,16 @@ 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). > Should we note the dependency on other factors as given in mhp_supports_memmap_on_memory(), especially, the system-wide setting and some weird kernel configurations?
On Fri, 2023-12-08 at 09:20 +0000, Zhijian Li (Fujitsu) wrote: > > > On 08/12/2023 03:25, Verma, Vishal L wrote: > > On Thu, 2023-12-07 at 08:29 +0000, Zhijian Li (Fujitsu) wrote: > > > Hi Vishal, > > > > > > > > > On 07/12/2023 12:36, Vishal Verma wrote: > > > > + > > > > +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 > > > > > > s/memmap_on+memory=1/memmap_on_memory=1 > > > > Thanks, will fix. > > > > > > > > > I have a question here > > > > > > What relationship about memmap_on_memory and 'ndctl-create-namespace > > > -M' option which > > > specifies where is the vmemmap backed memory. > > > I'm confused that memmap_on_memory=1 and '-M dev' are the same for > > > nvdimm devdax mode ? > > > > > The main difference is that memory that comes from non-nvdimm sources, > > such as hmem, or cxl, doesn't have a chance to set up the altmaps as > > pmem can with '-M dev'. For these, memmap_on_memory does this as part > > of the memory hotplug. > > Thanks for your explanation. > (I wrongly thought nvdimm.kmem was also controlled by '-M dev' before) > > feel free add: > Tested-by: Li Zhijian <lizhijian@fujitsu.com> Thank you Zhijian!
On Fri, 2023-12-08 at 11:13 +0800, Huang, Ying wrote: > Vishal Verma <vishal.l.verma@intel.com> writes: > [..] > > > > + > > +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_region *dax_region = dev_dax->region; > > + 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) { > > This still doesn't look right. Can we check whether the current driver > is kmem? And only allow change if it's not kmem? Ah yes I lost track of this todo between revisions when I split this out. Let me fix that for the next revision.
On Fri, 2023-12-08 at 12:36 +0100, David Hildenbrand wrote: > On 07.12.23 05:36, Vishal Verma wrote: [..] > > > > + > > +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). > > > > Should we note the dependency on other factors as given in > mhp_supports_memmap_on_memory(), especially, the system-wide setting and > some weird kernel configurations? > Yep good idea, I'll make a note of those for v3.
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c index 1ff1ab5fa105..11abb57cc031 100644 --- a/drivers/dax/bus.c +++ b/drivers/dax/bus.c @@ -1270,6 +1270,45 @@ 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_region *dax_region = dev_dax->region; + 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; + } + + device_lock(dev); + dev_dax->memmap_on_memory = val; + device_unlock(dev); + + device_unlock(dax_region->dev); + return rc == 0 ? len : rc; +} +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 +1335,7 @@ 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..bb063a004e41 100644 --- a/Documentation/ABI/testing/sysfs-bus-dax +++ b/Documentation/ABI/testing/sysfs-bus-dax @@ -149,3 +149,16 @@ 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).