Subject: [PATCH v7 0/7] Support new pmem flush and sync instructions for POWER

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 1 Jul 2020 12:52:28 +0530

This patch series enables the usage os new pmem flush and sync instructions on POWER
architecture. POWER10 introduces two new variants of dcbf instructions (dcbstps and dcbfps)
that can be used to write modified locations back to persistent storage. Additionally,
POWER10 also introduce phwsync and plwsync which can be used to establish order of these
writes to persistent storage.
    
This series exposes these instructions to the rest of the kernel. The existing
dcbf and hwsync instructions in P8 and P9 are adequate to enable appropriate
synchronization with OpenCAPI-hosted persistent storage. Hence the new instructions
are added as a variant of the old ones that old hardware won't differentiate.

On POWER10, pmem devices will be represented by a different device tree compat
strings. This ensures that older kernels won't initialize pmem devices on POWER10.

With this:
1) vPMEM continues to work since it is a volatile region. That 
doesn't need any flush instructions.

2) pmdk and other user applications get updated to use new instructions
and updated packages are made available to all distributions

3) On newer hardware, the device will appear with a new compat string. 
Hence older distributions won't initialize pmem on newer hardware.

Changes from v6:
* rename flush barrier to pmem_wmb(). Update documentation. 
* Drop the WARN_ON in flush routines.
* Drop pap_scm ndr_region flush callback.

Changes from v5:
* Drop CONFIG_ARCH_MAP_SYNC_DISABLE and related changes

Changes from V4:
* Add namespace specific sychronous fault control.

Changes from V3:
* Add new compat string to be used for the device.
* Use arch_pmem_flush_barrier() in dm-writecache.
Aneesh Kumar K.V (7):
  powerpc/pmem: Restrict papr_scm to P8 and above.
  powerpc/pmem: Add new instructions for persistent storage and sync
  powerpc/pmem: Add flush routines using new pmem store and sync
    instruction
  libnvdimm/nvdimm/flush: Allow architecture to override the flush
    barrier
  powerpc/pmem: Update ppc64 to use the new barrier instruction.
  powerpc/pmem: Avoid the barrier in flush routines
  powerpc/pmem: Initialize pmem device on newer hardware

 Documentation/memory-barriers.txt         | 14 ++++++++
 arch/powerpc/include/asm/barrier.h        | 13 +++++++
 arch/powerpc/include/asm/cacheflush.h     |  1 +
 arch/powerpc/include/asm/ppc-opcode.h     | 12 +++++++
 arch/powerpc/lib/pmem.c                   | 44 ++++++++++++++++++++---
 arch/powerpc/platforms/pseries/papr_scm.c |  1 +
 arch/powerpc/platforms/pseries/pmem.c     |  6 ++++
 drivers/md/dm-writecache.c                |  2 +-
 drivers/nvdimm/of_pmem.c                  |  1 +
 drivers/nvdimm/region_devs.c              |  8 ++---
 include/asm-generic/barrier.h             | 10 ++++++
 11 files changed, 103 insertions(+), 9 deletions(-)

-- 
2.26.2