[00/12] device-dax: Support sub-dividing soft-reserved ranges

Message

Dan Williams March 23, 2020, 11:54 p.m. UTC

The device-dax facility allows an address range to be directly mapped
through a chardev, or turned around and hotplugged to the core kernel
page allocator as System-RAM. It is the baseline mechanism for
converting persistent memory (pmem) to be used as another volatile
memory pool i.e. the current Memory Tiering hot topic on linux-mm.

In the case of pmem the nvdimm-namespace-label mechanism can sub-divide
it, but that labeling mechanism is not available / applicable to
soft-reserved ("EFI specific purpose") memory [1]. This series provides
a sysfs-mechanism for the daxctl utility to enable provisioning of
volatile-soft-reserved memory ranges.

The motivations for this facility are:

1/ Allow performance differentiated memory ranges to be split between
   kernel-managed and directly-accessed use cases.

2/ Allow physical memory to be provisioned along performance relevant
   address boundaries. For example, divide a memory-side cache [2] along
   cache-color boundaries.

3/ Parcel out soft-reserved memory to VMs using device-dax as a security
   / permissions boundary [3]. Specifically I have seen people (ab)using
   memmap=nn!ss (mark System-RAM as Peristent Memory) just to get the
   device-dax interface on custom address ranges.

The baseline for this series is today's next/master + "[PATCH v2 0/6]
Manual definition of Soft Reserved memory devices" [4].

Big thanks to Joao for the early testing and feedback on this series!

Given the dependencies on the memremap_pages() reworks in Andrew's tree
and the proximity to v5.7 this is clearly v5.8 material. The patches in
most need of a second opinion are the memremap_pages() reworks to switch
from 'struct resource' to 'struct range' and allow for an array of
ranges to be mapped at once.

[1]: https://lore.kernel.org/r/[e-mail]/
[2]: https://lore.kernel.org/r/[e-mail]/
[3]: https://lore.kernel.org/r/[e-mail]/
[4]: http://lore.kernel.org/r/[e-mail]/

---

Dan Williams (12):
      device-dax: Drop the dax_region.pfn_flags attribute
      device-dax: Move instance creation parameters to 'struct dev_dax_data'
      device-dax: Make pgmap optional for instance creation
      device-dax: Kill dax_kmem_res
      device-dax: Add an allocation interface for device-dax instances
      device-dax: Introduce seed devices
      drivers/base: Make device_find_child_by_name() compatible with sysfs inputs
      device-dax: Add resize support
      mm/memremap_pages: Convert to 'struct range'
      mm/memremap_pages: Support multiple ranges per invocation
      device-dax: Add dis-contiguous resource support
      device-dax: Introduce 'mapping' devices


 arch/powerpc/kvm/book3s_hv_uvmem.c     |   14 -
 drivers/base/core.c                    |    2 
 drivers/dax/bus.c                      |  877 ++++++++++++++++++++++++++++++--
 drivers/dax/bus.h                      |   28 +
 drivers/dax/dax-private.h              |   36 +
 drivers/dax/device.c                   |   97 ++--
 drivers/dax/hmem/hmem.c                |   18 -
 drivers/dax/kmem.c                     |  170 +++---
 drivers/dax/pmem/compat.c              |    2 
 drivers/dax/pmem/core.c                |   22 +
 drivers/gpu/drm/nouveau/nouveau_dmem.c |    4 
 drivers/nvdimm/badrange.c              |   26 -
 drivers/nvdimm/claim.c                 |   13 
 drivers/nvdimm/nd.h                    |    3 
 drivers/nvdimm/pfn_devs.c              |   13 
 drivers/nvdimm/pmem.c                  |   27 +
 drivers/nvdimm/region.c                |   21 -
 drivers/pci/p2pdma.c                   |   12 
 include/linux/memremap.h               |    9 
 include/linux/range.h                  |    6 
 mm/memremap.c                          |  297 ++++++-----
 tools/testing/nvdimm/dax-dev.c         |   22 +
 tools/testing/nvdimm/test/iomap.c      |    2 
 23 files changed, 1318 insertions(+), 403 deletions(-)