![Dan Williams](/assets/img/avatar_default.png)
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>
206 lines
5.8 KiB
C
206 lines
5.8 KiB
C
/*
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* Copyright(c) 2015 Intel Corporation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#ifndef __PMEM_H__
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#define __PMEM_H__
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#include <linux/io.h>
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#include <linux/uio.h>
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#ifdef CONFIG_ARCH_HAS_PMEM_API
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#define ARCH_MEMREMAP_PMEM MEMREMAP_WB
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#include <asm/pmem.h>
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#else
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#define ARCH_MEMREMAP_PMEM MEMREMAP_WT
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/*
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* These are simply here to enable compilation, all call sites gate
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* calling these symbols with arch_has_pmem_api() and redirect to the
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* implementation in asm/pmem.h.
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*/
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static inline bool __arch_has_wmb_pmem(void)
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{
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return false;
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}
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static inline void arch_wmb_pmem(void)
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{
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BUG();
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}
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static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
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size_t n)
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{
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BUG();
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}
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static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
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struct iov_iter *i)
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{
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BUG();
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return 0;
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}
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static inline void arch_clear_pmem(void __pmem *addr, size_t size)
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{
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BUG();
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}
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#endif
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/*
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* Architectures that define ARCH_HAS_PMEM_API must provide
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* implementations for arch_memcpy_to_pmem(), arch_wmb_pmem(),
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* arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem().
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*/
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static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size)
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{
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memcpy(dst, (void __force const *) src, size);
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}
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static inline void memunmap_pmem(struct device *dev, void __pmem *addr)
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{
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devm_memunmap(dev, (void __force *) addr);
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}
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static inline bool arch_has_pmem_api(void)
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{
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return IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API);
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}
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/**
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* arch_has_wmb_pmem - true if wmb_pmem() ensures durability
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*
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* For a given cpu implementation within an architecture it is possible
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* that wmb_pmem() resolves to a nop. In the case this returns
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* false, pmem api users are unable to ensure durability and may want to
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* fall back to a different data consistency model, or otherwise notify
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* the user.
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*/
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static inline bool arch_has_wmb_pmem(void)
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{
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return arch_has_pmem_api() && __arch_has_wmb_pmem();
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}
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/*
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* These defaults seek to offer decent performance and minimize the
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* window between i/o completion and writes being durable on media.
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* However, it is undefined / architecture specific whether
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* default_memremap_pmem + default_memcpy_to_pmem is sufficient for
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* making data durable relative to i/o completion.
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*/
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static inline void default_memcpy_to_pmem(void __pmem *dst, const void *src,
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size_t size)
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{
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memcpy((void __force *) dst, src, size);
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}
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static inline size_t default_copy_from_iter_pmem(void __pmem *addr,
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size_t bytes, struct iov_iter *i)
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{
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return copy_from_iter_nocache((void __force *)addr, bytes, i);
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}
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static inline void default_clear_pmem(void __pmem *addr, size_t size)
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{
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if (size == PAGE_SIZE && ((unsigned long)addr & ~PAGE_MASK) == 0)
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clear_page((void __force *)addr);
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else
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memset((void __force *)addr, 0, size);
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}
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/**
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* memremap_pmem - map physical persistent memory for pmem api
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* @offset: physical address of persistent memory
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* @size: size of the mapping
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*
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* Establish a mapping of the architecture specific memory type expected
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* by memcpy_to_pmem() and wmb_pmem(). For example, it may be
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* the case that an uncacheable or writethrough mapping is sufficient,
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* or a writeback mapping provided memcpy_to_pmem() and
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* wmb_pmem() arrange for the data to be written through the
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* cache to persistent media.
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*/
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static inline void __pmem *memremap_pmem(struct device *dev,
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resource_size_t offset, unsigned long size)
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{
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return (void __pmem *) devm_memremap(dev, offset, size,
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ARCH_MEMREMAP_PMEM);
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}
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/**
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* memcpy_to_pmem - copy data to persistent memory
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* @dst: destination buffer for the copy
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* @src: source buffer for the copy
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* @n: length of the copy in bytes
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*
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* Perform a memory copy that results in the destination of the copy
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* being effectively evicted from, or never written to, the processor
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* cache hierarchy after the copy completes. After memcpy_to_pmem()
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* data may still reside in cpu or platform buffers, so this operation
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* must be followed by a wmb_pmem().
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*/
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static inline void memcpy_to_pmem(void __pmem *dst, const void *src, size_t n)
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{
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if (arch_has_pmem_api())
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arch_memcpy_to_pmem(dst, src, n);
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else
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default_memcpy_to_pmem(dst, src, n);
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}
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/**
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* wmb_pmem - synchronize writes to persistent memory
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*
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* After a series of memcpy_to_pmem() operations this drains data from
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* cpu write buffers and any platform (memory controller) buffers to
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* ensure that written data is durable on persistent memory media.
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*/
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static inline void wmb_pmem(void)
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{
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if (arch_has_wmb_pmem())
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arch_wmb_pmem();
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else
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wmb();
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}
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/**
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* copy_from_iter_pmem - copy data from an iterator to PMEM
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* @addr: PMEM destination address
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* @bytes: number of bytes to copy
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* @i: iterator with source data
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*
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* Copy data from the iterator 'i' to the PMEM buffer starting at 'addr'.
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* This function requires explicit ordering with a wmb_pmem() call.
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*/
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static inline size_t copy_from_iter_pmem(void __pmem *addr, size_t bytes,
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struct iov_iter *i)
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{
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if (arch_has_pmem_api())
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return arch_copy_from_iter_pmem(addr, bytes, i);
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return default_copy_from_iter_pmem(addr, bytes, i);
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}
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/**
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* clear_pmem - zero a PMEM memory range
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* @addr: virtual start address
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* @size: number of bytes to zero
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*
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* Write zeros into the memory range starting at 'addr' for 'size' bytes.
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* This function requires explicit ordering with a wmb_pmem() call.
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*/
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static inline void clear_pmem(void __pmem *addr, size_t size)
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{
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if (arch_has_pmem_api())
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arch_clear_pmem(addr, size);
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else
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default_clear_pmem(addr, size);
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}
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#endif /* __PMEM_H__ */
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