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![Dan Williams](/assets/img/avatar_default.png)
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>
196 lines
5.2 KiB
C
196 lines
5.2 KiB
C
#ifndef _ASM_X86_UACCESS_64_H
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#define _ASM_X86_UACCESS_64_H
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/*
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* User space memory access functions
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*/
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#include <linux/compiler.h>
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#include <linux/lockdep.h>
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#include <linux/kasan-checks.h>
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#include <asm/alternative.h>
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#include <asm/cpufeatures.h>
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#include <asm/page.h>
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/*
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* Copy To/From Userspace
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*/
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/* Handles exceptions in both to and from, but doesn't do access_ok */
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__must_check unsigned long
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copy_user_enhanced_fast_string(void *to, const void *from, unsigned len);
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__must_check unsigned long
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copy_user_generic_string(void *to, const void *from, unsigned len);
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__must_check unsigned long
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copy_user_generic_unrolled(void *to, const void *from, unsigned len);
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static __always_inline __must_check unsigned long
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copy_user_generic(void *to, const void *from, unsigned len)
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{
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unsigned ret;
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/*
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* If CPU has ERMS feature, use copy_user_enhanced_fast_string.
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* Otherwise, if CPU has rep_good feature, use copy_user_generic_string.
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* Otherwise, use copy_user_generic_unrolled.
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*/
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alternative_call_2(copy_user_generic_unrolled,
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copy_user_generic_string,
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X86_FEATURE_REP_GOOD,
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copy_user_enhanced_fast_string,
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X86_FEATURE_ERMS,
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ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from),
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"=d" (len)),
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"1" (to), "2" (from), "3" (len)
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: "memory", "rcx", "r8", "r9", "r10", "r11");
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return ret;
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}
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static __always_inline __must_check unsigned long
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raw_copy_from_user(void *dst, const void __user *src, unsigned long size)
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{
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int ret = 0;
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if (!__builtin_constant_p(size))
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return copy_user_generic(dst, (__force void *)src, size);
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switch (size) {
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case 1:
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__uaccess_begin();
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__get_user_asm_nozero(*(u8 *)dst, (u8 __user *)src,
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ret, "b", "b", "=q", 1);
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__uaccess_end();
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return ret;
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case 2:
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__uaccess_begin();
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__get_user_asm_nozero(*(u16 *)dst, (u16 __user *)src,
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ret, "w", "w", "=r", 2);
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__uaccess_end();
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return ret;
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case 4:
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__uaccess_begin();
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__get_user_asm_nozero(*(u32 *)dst, (u32 __user *)src,
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ret, "l", "k", "=r", 4);
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__uaccess_end();
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return ret;
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case 8:
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__uaccess_begin();
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__get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 8);
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__uaccess_end();
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return ret;
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case 10:
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__uaccess_begin();
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__get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 10);
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if (likely(!ret))
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__get_user_asm_nozero(*(u16 *)(8 + (char *)dst),
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(u16 __user *)(8 + (char __user *)src),
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ret, "w", "w", "=r", 2);
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__uaccess_end();
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return ret;
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case 16:
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__uaccess_begin();
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__get_user_asm_nozero(*(u64 *)dst, (u64 __user *)src,
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ret, "q", "", "=r", 16);
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if (likely(!ret))
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__get_user_asm_nozero(*(u64 *)(8 + (char *)dst),
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(u64 __user *)(8 + (char __user *)src),
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ret, "q", "", "=r", 8);
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__uaccess_end();
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return ret;
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default:
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return copy_user_generic(dst, (__force void *)src, size);
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}
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}
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static __always_inline __must_check unsigned long
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raw_copy_to_user(void __user *dst, const void *src, unsigned long size)
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{
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int ret = 0;
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if (!__builtin_constant_p(size))
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return copy_user_generic((__force void *)dst, src, size);
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switch (size) {
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case 1:
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__uaccess_begin();
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__put_user_asm(*(u8 *)src, (u8 __user *)dst,
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ret, "b", "b", "iq", 1);
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__uaccess_end();
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return ret;
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case 2:
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__uaccess_begin();
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__put_user_asm(*(u16 *)src, (u16 __user *)dst,
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ret, "w", "w", "ir", 2);
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__uaccess_end();
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return ret;
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case 4:
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__uaccess_begin();
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__put_user_asm(*(u32 *)src, (u32 __user *)dst,
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ret, "l", "k", "ir", 4);
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__uaccess_end();
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return ret;
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case 8:
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__uaccess_begin();
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__put_user_asm(*(u64 *)src, (u64 __user *)dst,
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ret, "q", "", "er", 8);
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__uaccess_end();
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return ret;
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case 10:
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__uaccess_begin();
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__put_user_asm(*(u64 *)src, (u64 __user *)dst,
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ret, "q", "", "er", 10);
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if (likely(!ret)) {
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asm("":::"memory");
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__put_user_asm(4[(u16 *)src], 4 + (u16 __user *)dst,
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ret, "w", "w", "ir", 2);
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}
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__uaccess_end();
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return ret;
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case 16:
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__uaccess_begin();
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__put_user_asm(*(u64 *)src, (u64 __user *)dst,
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ret, "q", "", "er", 16);
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if (likely(!ret)) {
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asm("":::"memory");
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__put_user_asm(1[(u64 *)src], 1 + (u64 __user *)dst,
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ret, "q", "", "er", 8);
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}
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__uaccess_end();
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return ret;
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default:
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return copy_user_generic((__force void *)dst, src, size);
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}
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}
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static __always_inline __must_check
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unsigned long raw_copy_in_user(void __user *dst, const void __user *src, unsigned long size)
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{
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return copy_user_generic((__force void *)dst,
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(__force void *)src, size);
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}
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extern long __copy_user_nocache(void *dst, const void __user *src,
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unsigned size, int zerorest);
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extern long __copy_user_flushcache(void *dst, const void __user *src, unsigned size);
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extern void memcpy_page_flushcache(char *to, struct page *page, size_t offset,
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size_t len);
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static inline int
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__copy_from_user_inatomic_nocache(void *dst, const void __user *src,
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unsigned size)
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{
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kasan_check_write(dst, size);
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return __copy_user_nocache(dst, src, size, 0);
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}
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static inline int
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__copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
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{
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kasan_check_write(dst, size);
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return __copy_user_flushcache(dst, src, size);
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}
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unsigned long
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copy_user_handle_tail(char *to, char *from, unsigned len);
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#endif /* _ASM_X86_UACCESS_64_H */
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