forked from Minki/linux
0aed55af88
The pmem driver has a need to transfer data with a persistent memory destination and be able to rely on the fact that the destination writes are not cached. It is sufficient for the writes to be flushed to a cpu-store-buffer (non-temporal / "movnt" in x86 terms), as we expect userspace to call fsync() to ensure data-writes have reached a power-fail-safe zone in the platform. The fsync() triggers a REQ_FUA or REQ_FLUSH to the pmem driver which will turn around and fence previous writes with an "sfence". Implement a __copy_from_user_inatomic_flushcache, memcpy_page_flushcache, and memcpy_flushcache, that guarantee that the destination buffer is not dirty in the cpu cache on completion. The new copy_from_iter_flushcache and sub-routines will be used to replace the "pmem api" (include/linux/pmem.h + arch/x86/include/asm/pmem.h). The availability of copy_from_iter_flushcache() and memcpy_flushcache() are gated by the CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE config symbol, and fallback to copy_from_iter_nocache() and plain memcpy() otherwise. This is meant to satisfy the concern from Linus that if a driver wants to do something beyond the normal nocache semantics it should be something private to that driver [1], and Al's concern that anything uaccess related belongs with the rest of the uaccess code [2]. The first consumer of this interface is a new 'copy_from_iter' dax operation so that pmem can inject cache maintenance operations without imposing this overhead on other dax-capable drivers. [1]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008364.html [2]: https://lists.01.org/pipermail/linux-nvdimm/2017-April/009942.html Cc: <x86@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Toshi Kani <toshi.kani@hpe.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Matthew Wilcox <mawilcox@microsoft.com> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
#ifndef _ASM_X86_STRING_64_H
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#define _ASM_X86_STRING_64_H
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#ifdef __KERNEL__
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#include <linux/jump_label.h>
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/* Written 2002 by Andi Kleen */
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/* Only used for special circumstances. Stolen from i386/string.h */
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static __always_inline void *__inline_memcpy(void *to, const void *from, size_t n)
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{
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unsigned long d0, d1, d2;
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asm volatile("rep ; movsl\n\t"
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"testb $2,%b4\n\t"
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"je 1f\n\t"
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"movsw\n"
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"1:\ttestb $1,%b4\n\t"
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"je 2f\n\t"
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"movsb\n"
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"2:"
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: "=&c" (d0), "=&D" (d1), "=&S" (d2)
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: "0" (n / 4), "q" (n), "1" ((long)to), "2" ((long)from)
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: "memory");
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return to;
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}
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/* Even with __builtin_ the compiler may decide to use the out of line
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function. */
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#define __HAVE_ARCH_MEMCPY 1
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extern void *memcpy(void *to, const void *from, size_t len);
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extern void *__memcpy(void *to, const void *from, size_t len);
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#ifndef CONFIG_KMEMCHECK
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#if (__GNUC__ == 4 && __GNUC_MINOR__ < 3) || __GNUC__ < 4
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#define memcpy(dst, src, len) \
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({ \
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size_t __len = (len); \
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void *__ret; \
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if (__builtin_constant_p(len) && __len >= 64) \
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__ret = __memcpy((dst), (src), __len); \
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else \
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__ret = __builtin_memcpy((dst), (src), __len); \
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__ret; \
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})
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#endif
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#else
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/*
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* kmemcheck becomes very happy if we use the REP instructions unconditionally,
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* because it means that we know both memory operands in advance.
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*/
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#define memcpy(dst, src, len) __inline_memcpy((dst), (src), (len))
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#endif
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#define __HAVE_ARCH_MEMSET
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void *memset(void *s, int c, size_t n);
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void *__memset(void *s, int c, size_t n);
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#define __HAVE_ARCH_MEMMOVE
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void *memmove(void *dest, const void *src, size_t count);
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void *__memmove(void *dest, const void *src, size_t count);
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int memcmp(const void *cs, const void *ct, size_t count);
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size_t strlen(const char *s);
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char *strcpy(char *dest, const char *src);
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char *strcat(char *dest, const char *src);
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int strcmp(const char *cs, const char *ct);
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#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
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/*
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* For files that not instrumented (e.g. mm/slub.c) we
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* should use not instrumented version of mem* functions.
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*/
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#undef memcpy
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#define memcpy(dst, src, len) __memcpy(dst, src, len)
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#define memmove(dst, src, len) __memmove(dst, src, len)
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#define memset(s, c, n) __memset(s, c, n)
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#endif
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#define __HAVE_ARCH_MEMCPY_MCSAFE 1
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__must_check int memcpy_mcsafe_unrolled(void *dst, const void *src, size_t cnt);
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DECLARE_STATIC_KEY_FALSE(mcsafe_key);
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/**
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* memcpy_mcsafe - copy memory with indication if a machine check happened
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*
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* @dst: destination address
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* @src: source address
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* @cnt: number of bytes to copy
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*
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* Low level memory copy function that catches machine checks
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* We only call into the "safe" function on systems that can
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* actually do machine check recovery. Everyone else can just
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* use memcpy().
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*
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* Return 0 for success, -EFAULT for fail
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*/
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static __always_inline __must_check int
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memcpy_mcsafe(void *dst, const void *src, size_t cnt)
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{
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#ifdef CONFIG_X86_MCE
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if (static_branch_unlikely(&mcsafe_key))
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return memcpy_mcsafe_unrolled(dst, src, cnt);
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else
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#endif
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memcpy(dst, src, cnt);
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return 0;
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}
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#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
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#define __HAVE_ARCH_MEMCPY_FLUSHCACHE 1
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void memcpy_flushcache(void *dst, const void *src, size_t cnt);
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#endif
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#endif /* __KERNEL__ */
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#endif /* _ASM_X86_STRING_64_H */
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