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authorDan Williams <dan.j.williams@intel.com>2015-08-24 18:29:38 -0400
committerDan Williams <dan.j.williams@intel.com>2015-08-27 19:40:59 -0400
commit96601adb745186ccbcf5b078d4756f13381ec2af (patch)
tree1dff922da6a102e55978278c8ad078f30a7384b8 /include/linux/pmem.h
parent41e94a851304f7acac840adec4004f8aeee53ad4 (diff)
downloadop-kernel-dev-96601adb745186ccbcf5b078d4756f13381ec2af.zip
op-kernel-dev-96601adb745186ccbcf5b078d4756f13381ec2af.tar.gz
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 'include/linux/pmem.h')
-rw-r--r--include/linux/pmem.h36
1 files changed, 22 insertions, 14 deletions
diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index a9d84bf..85f810b3 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -17,16 +17,23 @@
#include <linux/uio.h>
#ifdef CONFIG_ARCH_HAS_PMEM_API
+#define ARCH_MEMREMAP_PMEM MEMREMAP_WB
#include <asm/pmem.h>
#else
-static inline void arch_wmb_pmem(void)
+#define ARCH_MEMREMAP_PMEM MEMREMAP_WT
+/*
+ * These are simply here to enable compilation, all call sites gate
+ * calling these symbols with arch_has_pmem_api() and redirect to the
+ * implementation in asm/pmem.h.
+ */
+static inline bool __arch_has_wmb_pmem(void)
{
- BUG();
+ return false;
}
-static inline bool arch_has_wmb_pmem(void)
+static inline void arch_wmb_pmem(void)
{
- return false;
+ BUG();
}
static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
@@ -53,7 +60,6 @@ static inline void arch_clear_pmem(void __pmem *addr, size_t size)
* implementations for arch_memcpy_to_pmem(), arch_wmb_pmem(),
* arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem().
*/
-
static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size)
{
memcpy(dst, (void __force const *) src, size);
@@ -64,8 +70,13 @@ static inline void memunmap_pmem(struct device *dev, void __pmem *addr)
devm_memunmap(dev, (void __force *) addr);
}
+static inline bool arch_has_pmem_api(void)
+{
+ return IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API);
+}
+
/**
- * arch_has_pmem_api - true if wmb_pmem() ensures durability
+ * arch_has_wmb_pmem - true if wmb_pmem() ensures durability
*
* For a given cpu implementation within an architecture it is possible
* that wmb_pmem() resolves to a nop. In the case this returns
@@ -73,9 +84,9 @@ static inline void memunmap_pmem(struct device *dev, void __pmem *addr)
* fall back to a different data consistency model, or otherwise notify
* the user.
*/
-static inline bool arch_has_pmem_api(void)
+static inline bool arch_has_wmb_pmem(void)
{
- return IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API) && arch_has_wmb_pmem();
+ return arch_has_pmem_api() && __arch_has_wmb_pmem();
}
/*
@@ -120,13 +131,8 @@ static inline void default_clear_pmem(void __pmem *addr, size_t size)
static inline void __pmem *memremap_pmem(struct device *dev,
resource_size_t offset, unsigned long size)
{
-#ifdef ARCH_MEMREMAP_PMEM
return (void __pmem *) devm_memremap(dev, offset, size,
ARCH_MEMREMAP_PMEM);
-#else
- return (void __pmem *) devm_memremap(dev, offset, size,
- MEMREMAP_WT);
-#endif
}
/**
@@ -158,8 +164,10 @@ static inline void memcpy_to_pmem(void __pmem *dst, const void *src, size_t n)
*/
static inline void wmb_pmem(void)
{
- if (arch_has_pmem_api())
+ if (arch_has_wmb_pmem())
arch_wmb_pmem();
+ else
+ wmb();
}
/**
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