qemu/docs/nvdimm.txt

15 way to create a vNVDIMM device at startup time is done via the
27  - "slots=$N" should be equal to or larger than the total amount of
30  - "maxmem=$MAX_SIZE" should be equal to or larger than the total size
36    $NVDIMM_SIZE on a file $PATH. All accesses to the virtual NVDIMM device go
37    to the file $PATH.
40    "share=on", then guest writes will be applied to the backend
42    "share=on", then above writes will be visible to it as well. If
43    "share=off", then guest writes won't be applied to the backend
44    file and thus will be invisible to other guests.
55    persistent writes. Linux guest drivers set the device to read-only when this
56    bit is present. Set unarmed to on when the memdev has readonly=on.
62 driver (e.g. "CONFIG_ACPI_NFIT=y" under Linux), it should be able to
68 1. Prior to QEMU v2.8.0, if memory-backend-file is used and the actual
69    backend file size is not equal to the size given by "size" option,
76    order to avoid the data corruption.
92 To enable label on vNVDIMM devices, users can simply add
93 "label-size=$SZ" option to "-device nvdimm", e.g.
105    will be inaccessible to the guest. If any useful data (e.g. the
114 devices. Similarly to the RAM hotplug, the vNVDIMM hotplug is
117 For example, the following commands add another 4GB vNVDIMM device to
140 QEMU uses mmap(2) to maps vNVDIMM backends and aligns the mapping
141 address to the page size (getpagesize(2)) by default. However, some
143 size. In that case, QEMU v2.12.0 and later provide 'align' option to
144 memory-backend-file to allow users to specify the proper alignment.
145 For device dax (e.g., /dev/dax0.0), this alignment needs to match the
147 must be larger than or equal to the 'align' of device dax.
148 We can use one of the following commands to show the 'align' of device dax.
153 In order to get the proper 'align' of device dax, you need to install
157 following QEMU command line options to use it (/dev/dax0.0) as the
176 both 'pmem' and 'share' flags are set to 'on' on the backend.
183 provided to test for them.
187 When using other types of backends, it's suggested to set 'unarmed'
188 option of '-device nvdimm' to 'on', which sets the unarmed flag of the
197 Here are two examples showing how to setup these persistent backends on
202 Use the following command to set up /dev/dax0.0 so that the entirety of
203 namespace0.0 can be exposed as an emulated NVDIMM to the guest:
227 which allows the platform to communicate what features it supports related to
228 NVDIMM data persistence.  Users can provide a persistence value to a guest via
236              controller to the NVDIMMs in the event of power loss.
238 "cpu"      - The platform supports flushing dirty data from the CPU cache to
244 SNIA NVM Programming Model [1] (e.g., Intel NVDIMM), it's suggested to set
245 the 'pmem' option of memory-backend-file to 'on'. When 'pmem' is 'on' and QEMU
247 will take necessary operations to guarantee the persistence of its own writes
248 to the vNVDIMM backend(e.g., in vNVDIMM label emulation and live migration).
250 a "lack of libpmem support" message to ensure the persistence is available.
251 For example, if we want to ensure the persistence for some backend file,