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author | Dan Williams <dan.j.williams@intel.com> | 2015-08-24 22:29:38 (GMT) |
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committer | Dan Williams <dan.j.williams@intel.com> | 2015-08-27 23:40:59 (GMT) |
commit | 96601adb745186ccbcf5b078d4756f13381ec2af (patch) | |
tree | 1dff922da6a102e55978278c8ad078f30a7384b8 /drivers/nvdimm/nd.h | |
parent | 41e94a851304f7acac840adec4004f8aeee53ad4 (diff) | |
download | linux-96601adb745186ccbcf5b078d4756f13381ec2af.tar.xz |
x86, pmem: clarify that ARCH_HAS_PMEM_API implies PMEM mapped WB
Given that a write-back (WB) mapping plus non-temporal stores is
expected to be the most efficient way to access PMEM, update the
definition of ARCH_HAS_PMEM_API to imply arch support for
WB-mapped-PMEM. This is needed as a pre-requisite for adding PMEM to
the direct map and mapping it with struct page.
The above clarification for X86_64 means that memcpy_to_pmem() is
permitted to use the non-temporal arch_memcpy_to_pmem() rather than
needlessly fall back to default_memcpy_to_pmem() when the pcommit
instruction is not available. When arch_memcpy_to_pmem() is not
guaranteed to flush writes out of cache, i.e. on older X86_32
implementations where non-temporal stores may just dirty cache,
ARCH_HAS_PMEM_API is simply disabled.
The default fall back for persistent memory handling remains. Namely,
map it with the WT (write-through) cache-type and hope for the best.
arch_has_pmem_api() is updated to only indicate whether the arch
provides the proper helpers to meet the minimum "writes are visible
outside the cache hierarchy after memcpy_to_pmem() + wmb_pmem()". Code
that cares whether wmb_pmem() actually flushes writes to pmem must now
call arch_has_wmb_pmem() directly.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
[hch: set ARCH_HAS_PMEM_API=n on x86_32]
Reviewed-by: Christoph Hellwig <hch@lst.de>
[toshi: x86_32 compile fixes]
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/nvdimm/nd.h')
0 files changed, 0 insertions, 0 deletions