arch/x86/include/asm/pmem.h

   1 /*
   2  * Copyright(c) 2015 Intel Corporation. All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  */
  13 #ifndef __ASM_X86_PMEM_H__
  14 #define __ASM_X86_PMEM_H__
  15
  16 #include <linux/uaccess.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/cpufeature.h>
  19 #include <asm/special_insns.h>
  20
  21 #ifdef CONFIG_ARCH_HAS_PMEM_API
  22 /**
  23  * arch_memcpy_to_pmem - copy data to persistent memory
  24  * @dst: destination buffer for the copy
  25  * @src: source buffer for the copy
  26  * @n: length of the copy in bytes
  27  *
  28  * Copy data to persistent memory media via non-temporal stores so that
  29  * a subsequent arch_wmb_pmem() can flush cpu and memory controller
  30  * write buffers to guarantee durability.
  31  */
  32 static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
  33                 size_t n)
  34 {
  35         int unwritten;
  36
  37         /*
  38          * We are copying between two kernel buffers, if
  39          * __copy_from_user_inatomic_nocache() returns an error (page
  40          * fault) we would have already reported a general protection fault
  41          * before the WARN+BUG.
  42          */
  43         unwritten = __copy_from_user_inatomic_nocache((void __force *) dst,
  44                         (void __user *) src, n);
  45         if (WARN(unwritten, "%s: fault copying %p <- %p unwritten: %d\n",
  46                                 __func__, dst, src, unwritten))
  47                 BUG();
  48 }
  49
  50 /**
  51  * arch_wmb_pmem - synchronize writes to persistent memory
  52  *
  53  * After a series of arch_memcpy_to_pmem() operations this drains data
  54  * from cpu write buffers and any platform (memory controller) buffers
  55  * to ensure that written data is durable on persistent memory media.
  56  */
  57 static inline void arch_wmb_pmem(void)
  58 {
  59         /*
  60          * wmb() to 'sfence' all previous writes such that they are
  61          * architecturally visible to 'pcommit'.  Note, that we've
  62          * already arranged for pmem writes to avoid the cache via
  63          * arch_memcpy_to_pmem().
  64          */
  65         wmb();
  66         pcommit_sfence();
  67 }
  68
  69 /**
  70  * __arch_wb_cache_pmem - write back a cache range with CLWB
  71  * @vaddr:      virtual start address
  72  * @size:       number of bytes to write back
  73  *
  74  * Write back a cache range using the CLWB (cache line write back)
  75  * instruction.  This function requires explicit ordering with an
  76  * arch_wmb_pmem() call.  This API is internal to the x86 PMEM implementation.
  77  */
  78 static inline void __arch_wb_cache_pmem(void *vaddr, size_t size)
  79 {
  80         u16 x86_clflush_size = boot_cpu_data.x86_clflush_size;
  81         unsigned long clflush_mask = x86_clflush_size - 1;
  82         void *vend = vaddr + size;
  83         void *p;
  84
  85         for (p = (void *)((unsigned long)vaddr & ~clflush_mask);
  86              p < vend; p += x86_clflush_size)
  87                 clwb(p);
  88 }
  89
  90 /*
  91  * copy_from_iter_nocache() on x86 only uses non-temporal stores for iovec
  92  * iterators, so for other types (bvec & kvec) we must do a cache write-back.
  93  */
  94 static inline bool __iter_needs_pmem_wb(struct iov_iter *i)
  95 {
  96         return iter_is_iovec(i) == false;
  97 }
  98
  99 /**
 100  * arch_copy_from_iter_pmem - copy data from an iterator to PMEM
 101  * @addr:       PMEM destination address
 102  * @bytes:      number of bytes to copy
 103  * @i:          iterator with source data
 104  *
 105  * Copy data from the iterator 'i' to the PMEM buffer starting at 'addr'.
 106  * This function requires explicit ordering with an arch_wmb_pmem() call.
 107  */
 108 static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
 109                 struct iov_iter *i)
 110 {
 111         void *vaddr = (void __force *)addr;
 112         size_t len;
 113
 114         /* TODO: skip the write-back by always using non-temporal stores */
 115         len = copy_from_iter_nocache(vaddr, bytes, i);
 116
 117         if (__iter_needs_pmem_wb(i))
 118                 __arch_wb_cache_pmem(vaddr, bytes);
 119
 120         return len;
 121 }
 122
 123 /**
 124  * arch_clear_pmem - zero a PMEM memory range
 125  * @addr:       virtual start address
 126  * @size:       number of bytes to zero
 127  *
 128  * Write zeros into the memory range starting at 'addr' for 'size' bytes.
 129  * This function requires explicit ordering with an arch_wmb_pmem() call.
 130  */
 131 static inline void arch_clear_pmem(void __pmem *addr, size_t size)
 132 {
 133         void *vaddr = (void __force *)addr;
 134
 135         /* TODO: implement the zeroing via non-temporal writes */
 136         if (size == PAGE_SIZE && ((unsigned long)vaddr & ~PAGE_MASK) == 0)
 137                 clear_page(vaddr);
 138         else
 139                 memset(vaddr, 0, size);
 140
 141         __arch_wb_cache_pmem(vaddr, size);
 142 }
 143
 144 static inline bool __arch_has_wmb_pmem(void)
 145 {
 146         /*
 147          * We require that wmb() be an 'sfence', that is only guaranteed on
 148          * 64-bit builds
 149          */
 150         return static_cpu_has(X86_FEATURE_PCOMMIT);
 151 }
 152 #endif /* CONFIG_ARCH_HAS_PMEM_API */
 153 #endif /* __ASM_X86_PMEM_H__ */