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Diffstat (limited to 'docs/nvdimm.txt')
| -rw-r--r-- | docs/nvdimm.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index 21249dd062..e903d8bb09 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -138,3 +138,18 @@ backend of vNVDIMM: -object memory-backend-file,id=mem1,share=on,mem-path=/dev/dax0.0,size=4G,align=2M -device nvdimm,id=nvdimm1,memdev=mem1 + +Guest Data Persistence +---------------------- + +Though QEMU supports multiple types of vNVDIMM backends on Linux, +currently the only one that can guarantee the guest write persistence +is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to +which all guest access do not involve any host-side kernel cache. + +When using other types of backends, it's suggested to set 'unarmed' +option of '-device nvdimm' to 'on', which sets the unarmed flag of the +guest NVDIMM region mapping structure. This unarmed flag indicates +guest software that this vNVDIMM device contains a region that cannot +accept persistent writes. In result, for example, the guest Linux +NVDIMM driver, marks such vNVDIMM device as read-only. |