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_wt, memcpy_page_wt, and memcpy_wt, that guarantee that the destination buffer is not dirty in the cpu cache on completion. The new copy_from_iter_wt 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_wt() and memcpy_wt() are gated by the CONFIG_ARCH_HAS_UACCESS_WT 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]. [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@xxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- Changes since the initial RFC: * s/writethru/wt/ since we already have ioremap_wt(), set_memory_wt(), etc. (Ingo) arch/x86/Kconfig | 1 arch/x86/include/asm/string_64.h | 5 + arch/x86/include/asm/uaccess_64.h | 11 +++ arch/x86/lib/usercopy_64.c | 128 +++++++++++++++++++++++++++++++++++++ drivers/acpi/nfit/core.c | 3 - drivers/nvdimm/claim.c | 2 - drivers/nvdimm/pmem.c | 13 +++- drivers/nvdimm/region_devs.c | 4 + include/linux/dax.h | 3 + include/linux/string.h | 6 ++ include/linux/uio.h | 15 ++++ lib/Kconfig | 3 + lib/iov_iter.c | 21 ++++++ 13 files changed, 208 insertions(+), 7 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1d50fdff77ee..398117923b1c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -54,6 +54,7 @@ config X86 select ARCH_HAS_KCOV if X86_64 select ARCH_HAS_MMIO_FLUSH select ARCH_HAS_PMEM_API if X86_64 + select ARCH_HAS_UACCESS_WT if X86_64 select ARCH_HAS_SET_MEMORY select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index 733bae07fb29..dfbd66b11c72 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -109,6 +109,11 @@ memcpy_mcsafe(void *dst, const void *src, size_t cnt) return 0; } +#ifdef CONFIG_ARCH_HAS_UACCESS_WT +#define __HAVE_ARCH_MEMCPY_WT 1 +void memcpy_wt(void *dst, const void *src, size_t cnt); +#endif + #endif /* __KERNEL__ */ #endif /* _ASM_X86_STRING_64_H */ diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index c5504b9a472e..07ded30c7e89 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -171,6 +171,10 @@ unsigned long raw_copy_in_user(void __user *dst, const void __user *src, unsigne extern long __copy_user_nocache(void *dst, const void __user *src, unsigned size, int zerorest); +extern long __copy_user_wt(void *dst, const void __user *src, unsigned size); +extern void memcpy_page_wt(char *to, struct page *page, size_t offset, + size_t len); + static inline int __copy_from_user_inatomic_nocache(void *dst, const void __user *src, unsigned size) @@ -179,6 +183,13 @@ __copy_from_user_inatomic_nocache(void *dst, const void __user *src, return __copy_user_nocache(dst, src, size, 0); } +static inline int +__copy_from_user_inatomic_wt(void *dst, const void __user *src, unsigned size) +{ + kasan_check_write(dst, size); + return __copy_user_wt(dst, src, size); +} + unsigned long copy_user_handle_tail(char *to, char *from, unsigned len); diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c index 3b7c40a2e3e1..0aeff66a022f 100644 --- a/arch/x86/lib/usercopy_64.c +++ b/arch/x86/lib/usercopy_64.c @@ -7,6 +7,7 @@ */ #include <linux/export.h> #include <linux/uaccess.h> +#include <linux/highmem.h> /* * Zero Userspace @@ -73,3 +74,130 @@ copy_user_handle_tail(char *to, char *from, unsigned len) clac(); return len; } + +#ifdef CONFIG_ARCH_HAS_UACCESS_WT +/** + * clean_cache_range - write back a cache range with CLWB + * @vaddr: virtual start address + * @size: number of bytes to write back + * + * Write back a cache range using the CLWB (cache line write back) + * instruction. Note that @size is internally rounded up to be cache + * line size aligned. + */ +static void clean_cache_range(void *addr, size_t size) +{ + u16 x86_clflush_size = boot_cpu_data.x86_clflush_size; + unsigned long clflush_mask = x86_clflush_size - 1; + void *vend = addr + size; + void *p; + + for (p = (void *)((unsigned long)addr & ~clflush_mask); + p < vend; p += x86_clflush_size) + clwb(p); +} + +long __copy_user_wt(void *dst, const void __user *src, unsigned size) +{ + unsigned long flushed, dest = (unsigned long) dst; + long rc = __copy_user_nocache(dst, src, size, 0); + + /* + * __copy_user_nocache() uses non-temporal stores for the bulk + * of the transfer, but we need to manually flush if the + * transfer is unaligned. A cached memory copy is used when + * destination or size is not naturally aligned. That is: + * - Require 8-byte alignment when size is 8 bytes or larger. + * - Require 4-byte alignment when size is 4 bytes. + */ + if (size < 8) { + if (!IS_ALIGNED(dest, 4) || size != 4) + clean_cache_range(dst, 1); + } else { + if (!IS_ALIGNED(dest, 8)) { + dest = ALIGN(dest, boot_cpu_data.x86_clflush_size); + clean_cache_range(dst, 1); + } + + flushed = dest - (unsigned long) dst; + if (size > flushed && !IS_ALIGNED(size - flushed, 8)) + clean_cache_range(dst + size - 1, 1); + } + + return rc; +} + +void memcpy_wt(void *_dst, const void *_src, size_t size) +{ + unsigned long dest = (unsigned long) _dst; + unsigned long source = (unsigned long) _src; + + /* cache copy and flush to align dest */ + if (!IS_ALIGNED(dest, 8)) { + unsigned len = min_t(unsigned, size, ALIGN(dest, 8) - dest); + + memcpy((void *) dest, (void *) source, len); + clean_cache_range((void *) dest, len); + dest += len; + source += len; + size -= len; + if (!size) + return; + } + + /* 4x8 movnti loop */ + while (size >= 32) { + asm("movq (%0), %%r8\n" + "movq 8(%0), %%r9\n" + "movq 16(%0), %%r10\n" + "movq 24(%0), %%r11\n" + "movnti %%r8, (%1)\n" + "movnti %%r9, 8(%1)\n" + "movnti %%r10, 16(%1)\n" + "movnti %%r11, 24(%1)\n" + :: "r" (source), "r" (dest) + : "memory", "r8", "r9", "r10", "r11"); + dest += 32; + source += 32; + size -= 32; + } + + /* 1x8 movnti loop */ + while (size >= 8) { + asm("movq (%0), %%r8\n" + "movnti %%r8, (%1)\n" + :: "r" (source), "r" (dest) + : "memory", "r8"); + dest += 8; + source += 8; + size -= 8; + } + + /* 1x4 movnti loop */ + while (size >= 4) { + asm("movl (%0), %%r8d\n" + "movnti %%r8d, (%1)\n" + :: "r" (source), "r" (dest) + : "memory", "r8"); + dest += 4; + source += 4; + size -= 4; + } + + /* cache copy for remaining bytes */ + if (size) { + memcpy((void *) dest, (void *) source, size); + clean_cache_range((void *) dest, size); + } +} +EXPORT_SYMBOL_GPL(memcpy_wt); + +void memcpy_page_wt(char *to, struct page *page, size_t offset, + size_t len) +{ + char *from = kmap_atomic(page); + + memcpy_wt(to, from + offset, len); + kunmap_atomic(from); +} +#endif diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c index d0c07b2344e4..be9bba609f26 100644 --- a/drivers/acpi/nfit/core.c +++ b/drivers/acpi/nfit/core.c @@ -1776,8 +1776,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk, } if (rw) - memcpy_to_pmem(mmio->addr.aperture + offset, - iobuf + copied, c); + memcpy_wt(mmio->addr.aperture + offset, iobuf + copied, c); else { if (nfit_blk->dimm_flags & NFIT_BLK_READ_FLUSH) mmio_flush_range((void __force *) diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c index 3a35e8028b9c..864ed42baaf0 100644 --- a/drivers/nvdimm/claim.c +++ b/drivers/nvdimm/claim.c @@ -266,7 +266,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns, rc = -EIO; } - memcpy_to_pmem(nsio->addr + offset, buf, size); + memcpy_wt(nsio->addr + offset, buf, size); nvdimm_flush(to_nd_region(ndns->dev.parent)); return rc; diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 3b3dab73d741..4be8f30de9b3 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -28,6 +28,7 @@ #include <linux/pfn_t.h> #include <linux/slab.h> #include <linux/pmem.h> +#include <linux/uio.h> #include <linux/dax.h> #include <linux/nd.h> #include "pmem.h" @@ -79,7 +80,7 @@ static void write_pmem(void *pmem_addr, struct page *page, { void *mem = kmap_atomic(page); - memcpy_to_pmem(pmem_addr, mem + off, len); + memcpy_wt(pmem_addr, mem + off, len); kunmap_atomic(mem); } @@ -234,8 +235,15 @@ static long pmem_dax_direct_access(struct dax_device *dax_dev, return __pmem_direct_access(pmem, pgoff, nr_pages, kaddr, pfn); } +static size_t pmem_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, + void *addr, size_t bytes, struct iov_iter *i) +{ + return copy_from_iter_wt(addr, bytes, i); +} + static const struct dax_operations pmem_dax_ops = { .direct_access = pmem_dax_direct_access, + .copy_from_iter = pmem_copy_from_iter, }; static void pmem_release_queue(void *q) @@ -288,7 +296,8 @@ static int pmem_attach_disk(struct device *dev, dev_set_drvdata(dev, pmem); pmem->phys_addr = res->start; pmem->size = resource_size(res); - if (nvdimm_has_flush(nd_region) < 0) + if (!IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_WT) + || nvdimm_has_flush(nd_region) < 0) dev_warn(dev, "unable to guarantee persistence of writes\n"); if (!devm_request_mem_region(dev, res->start, resource_size(res), diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c index b7cb5066d961..016af2a6694d 100644 --- a/drivers/nvdimm/region_devs.c +++ b/drivers/nvdimm/region_devs.c @@ -947,8 +947,8 @@ void nvdimm_flush(struct nd_region *nd_region) * The first wmb() is needed to 'sfence' all previous writes * such that they are architecturally visible for the platform * buffer flush. Note that we've already arranged for pmem - * writes to avoid the cache via arch_memcpy_to_pmem(). The - * final wmb() ensures ordering for the NVDIMM flush write. + * writes to avoid the cache via memcpy_wt(). The final wmb() + * ensures ordering for the NVDIMM flush write. */ wmb(); for (i = 0; i < nd_region->ndr_mappings; i++) diff --git a/include/linux/dax.h b/include/linux/dax.h index d3158e74a59e..156f067d4db5 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -16,6 +16,9 @@ struct dax_operations { */ long (*direct_access)(struct dax_device *, pgoff_t, long, void **, pfn_t *); + /* copy_from_iter: dax-driver override for default copy_from_iter */ + size_t (*copy_from_iter)(struct dax_device *, pgoff_t, void *, size_t, + struct iov_iter *); }; int dax_read_lock(void); diff --git a/include/linux/string.h b/include/linux/string.h index 9d6f189157e2..245e0a29b7e5 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -122,6 +122,12 @@ static inline __must_check int memcpy_mcsafe(void *dst, const void *src, return 0; } #endif +#ifndef __HAVE_ARCH_MEMCPY_WT +static inline void memcpy_wt(void *dst, const void *src, size_t cnt) +{ + memcpy(dst, src, cnt); +} +#endif void *memchr_inv(const void *s, int c, size_t n); char *strreplace(char *s, char old, char new); diff --git a/include/linux/uio.h b/include/linux/uio.h index f2d36a3d3005..30c43aa371b5 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -95,6 +95,21 @@ size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i); size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i); bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i); size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i); +#ifdef CONFIG_ARCH_HAS_UACCESS_WT +/* + * Note, users like pmem that depend on the stricter semantics of + * copy_from_iter_wt() than copy_from_iter_nocache() must check + * for IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_WRITETHROUGH) before assuming + * that the destination is flushed from the cache on return. + */ +size_t copy_from_iter_wt(void *addr, size_t bytes, struct iov_iter *i); +#else +static inline size_t copy_from_iter_wt(void *addr, size_t bytes, + struct iov_iter *i) +{ + return copy_from_iter_nocache(addr, bytes, i); +} +#endif bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i); size_t iov_iter_zero(size_t bytes, struct iov_iter *); unsigned long iov_iter_alignment(const struct iov_iter *i); diff --git a/lib/Kconfig b/lib/Kconfig index 0c8b78a9ae2e..f0752a7a9001 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -548,6 +548,9 @@ config ARCH_HAS_SG_CHAIN config ARCH_HAS_PMEM_API bool +config ARCH_HAS_UACCESS_WT + bool + config ARCH_HAS_MMIO_FLUSH bool diff --git a/lib/iov_iter.c b/lib/iov_iter.c index f7c93568ec99..19ab9af091f9 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -615,6 +615,27 @@ size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i) } EXPORT_SYMBOL(copy_from_iter_nocache); +#ifdef CONFIG_ARCH_HAS_UACCESS_WT +size_t copy_from_iter_wt(void *addr, size_t bytes, struct iov_iter *i) +{ + char *to = addr; + if (unlikely(i->type & ITER_PIPE)) { + WARN_ON(1); + return 0; + } + iterate_and_advance(i, bytes, v, + __copy_from_user_inatomic_wt((to += v.iov_len) - v.iov_len, + v.iov_base, v.iov_len), + memcpy_page_wt((to += v.bv_len) - v.bv_len, v.bv_page, + v.bv_offset, v.bv_len), + memcpy_wt((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len) + ) + + return bytes; +} +EXPORT_SYMBOL_GPL(copy_from_iter_wt); +#endif + bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i) { char *to = addr;
