| From: |
| Mike Rapoport <rppt-AT-kernel.org> |
| To: |
| Dan Williams <dan.j.williams-AT-intel.com>, Dave Jiang <dave.jiang-AT-intel.com>, Ira Weiny <ira.weiny-AT-intel.com>, Vishal Verma <vishal.l.verma-AT-intel.com> |
| Subject: |
| [PATCH v2 0/1] nvdimm: allow exposing RAM as libnvdimm DIMMs |
| Date: |
| Wed, 15 Oct 2025 11:00:19 +0300 |
| Message-ID: |
| <20251015080020.3018581-1-rppt@kernel.org> |
| Cc: |
| jane.chu-AT-oracle.com, Michał Cłapiński <mclapinski-AT-google.com>, Mike Rapoport <rppt-AT-kernel.org>, Pasha Tatashin <pasha.tatashin-AT-soleen.com>, Tyler Hicks <code-AT-tyhicks.com>, linux-kernel-AT-vger.kernel.org, nvdimm-AT-lists.linux.dev |
| Archive-link: |
| Article |
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
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.
v2 changes:
* 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/20250826080430.1952982-1-rppt...
* 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/20250612083153.48624-1-rppt@k...
Mike Rapoport (Microsoft) (1):
nvdimm: allow exposing RAM carveouts as NVDIMM DIMM devices
drivers/nvdimm/Kconfig | 17 +++
drivers/nvdimm/Makefile | 1 +
drivers/nvdimm/ramdax.c | 272 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 290 insertions(+)
create mode 100644 drivers/nvdimm/ramdax.c
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
--
2.50.1
