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| author |   Dan Williams <dan.j.williams@intel.com> | 2015-08-24 18:29:38 -0400 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2015-08-27 19:40:59 -0400 |
| commit | 96601adb745186ccbcf5b078d4756f13381ec2af (patch) | |
| tree | 1dff922da6a102e55978278c8ad078f30a7384b8 /drivers/acpi | |
| parent | add devm_memremap_pages (diff) | |
| download | linux-dev-96601adb745186ccbcf5b078d4756f13381ec2af.tar.xz linux-dev-96601adb745186ccbcf5b078d4756f13381ec2af.zip | |
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/acpi')
| -rw-r--r-- | drivers/acpi/nfit.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c index 56fff0141636..f61e69fa2ad1 100644 --- a/drivers/acpi/nfit.c +++ b/drivers/acpi/nfit.c @@ -20,6 +20,7 @@ #include <linux/sort.h> #include <linux/pmem.h> #include <linux/io.h> +#include <asm/cacheflush.h> #include "nfit.h" /* @@ -1371,7 +1372,7 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus, return -ENOMEM; } - if (!arch_has_pmem_api() && !nfit_blk->nvdimm_flush) + if (!arch_has_wmb_pmem() && !nfit_blk->nvdimm_flush) dev_warn(dev, "unable to guarantee persistence of writes\n"); if (mmio->line_size == 0) |