From: "Mike Rapoport (Microsoft)" <[email protected]> Hi,
It's not uncommon that libnvdimm/dax/ndctl are used with normal volatile memory for a whole bunch of $reasons. Probably the most common usecase is to back VMs memory with fsdax/devdax, but there are others as well when there's a requirement to manage memory separately from the kernel. The existing mechanisms to expose normal ram as "persistent", such as memmap=x!y on x86 or dummy pmem-region device tree nodes on DT systems lack flexibility to dynamically partition a single region without rebooting the system and sometimes even updating the system firmware. Also, to create several DAX devices with different properties it's necessary to repeat the memmap= command line option or add several pmem-region nodes to the DT. I propose a new ramdax driver that will create a DIMM device on E820_TYPE_PRAM/pmem-region and that will allow partitioning that device dynamically. The label area is kept in the end of that region and managed by the driver. v3 changes: * Update Kconfig dependencies and help text * Add manual check for of_match_node() * Adjust white space for function parameters to match other nvdimm drivers * Add Reviewed-by, thanks Dan! v2: https://lore.kernel.org/all/[email protected] * Change the way driver is bound to a device, following Dan's suggestion. Instead of forcing mutual exclusion of ramdax and nr_e820/of-pmem at build time, rely on 'driver_override' attribute to allow binding ramdax driver to e820_pmem/pmem-region devices. * Fix build warning reported by kbuild v1: https://lore.kernel.org/all/[email protected] * fix offset calculations in ramdax_{get,set}_config_data * use a magic constant instead of a random number as nd_set->cookie* RFC: https://lore.kernel.org/all/[email protected] Mike Rapoport (Microsoft) (1): nvdimm: allow exposing RAM carveouts as NVDIMM DIMM devices drivers/nvdimm/Kconfig | 19 +++ drivers/nvdimm/Makefile | 1 + drivers/nvdimm/ramdax.c | 282 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 302 insertions(+) create mode 100644 drivers/nvdimm/ramdax.c base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787 -- 2.50.1
