From 96601adb745186ccbcf5b078d4756f13381ec2af Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 24 Aug 2015 18:29:38 -0400 Subject: 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 Cc: Ingo Molnar Cc: "H. Peter Anvin" Reviewed-by: Ross Zwisler [hch: set ARCH_HAS_PMEM_API=n on x86_32] Reviewed-by: Christoph Hellwig [toshi: x86_32 compile fixes] Signed-off-by: Toshi Kani Signed-off-by: Dan Williams --- drivers/nvdimm/pmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/nvdimm') diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 3b5b9cb758b6..20bf122328da 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -125,7 +125,7 @@ static struct pmem_device *pmem_alloc(struct device *dev, pmem->phys_addr = res->start; pmem->size = resource_size(res); - if (!arch_has_pmem_api()) + if (!arch_has_wmb_pmem()) dev_warn(dev, "unable to guarantee persistence of writes\n"); if (!devm_request_mem_region(dev, pmem->phys_addr, pmem->size, -- cgit v1.2.3