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Date: Thu, 18 Feb 2016 13:33:15 -0800 From: Dan Williams <dan.j.williams@...el.com> To: Ingo Molnar <mingo@...nel.org> Cc: "Luck, Tony" <tony.luck@...el.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() On Thu, Feb 18, 2016 at 12:14 PM, Ingo Molnar <mingo@...nel.org> wrote: > > * Luck, Tony <tony.luck@...el.com> wrote: > >> On Thu, Feb 18, 2016 at 10:12:42AM -0800, Linus Torvalds wrote: >> > On Wed, Feb 17, 2016 at 10:20 AM, Tony Luck <tony.luck@...el.com> wrote: >> > > >> > > If we faulted during the copy, then 'trapnr' will say which type >> > > of trap (X86_TRAP_PF or X86_TRAP_MC) and 'remain' says how many >> > > bytes were not copied. >> > >> > So apart from the naming, a couple of questions: >> > >> > - I'd like to see the actual *use* case explained, not just what it does. >> >> First user is libnvdimm. Dan Williams already has code to use this so that >> kernel code accessing persistent memory can return -EIO to a user instead of >> crashing the system if the cpu runs into an uncorrected error during the copy. > > Are these the memcpy_*_pmem() calls in drivers/nvdimm/pmem.c? Is there any actual > patch to look at? > Here's the integration patch I had from the version of mcsafe_copy() at the beginning of January. Pardon the whitespace damage... the original thread is here: [1]. Note that the "badblocks" intergration portion of that set went upstream in v4.5-rc1. [1]: https://lists.01.org/pipermail/linux-nvdimm/2016-January/003864.html --- Subject: x86, pmem: use __mcsafe_copy() for memcpy_from_pmem() In support of large capacity persistent memory use __mcsafe_copy() for pmem I/O. This allows the pmem driver to support an error model similar to disks when machine check recovery is available. Cc: Thomas Gleixner <tglx@...utronix.de> Cc: Ingo Molnar <mingo@...hat.com> Cc: "H. Peter Anvin" <hpa@...or.com> Cc: x86@...nel.org Cc: Borislav Petkov <bp@...e.de> Cc: Tony Luck <tony.luck@...el.com> Cc: Andy Lutomirski <luto@...capital.net> Signed-off-by: Dan Williams <dan.j.williams@...el.com> --- arch/x86/include/asm/pmem.h | 16 ++++++++++++++++ drivers/nvdimm/Kconfig | 1 + drivers/nvdimm/pmem.c | 10 ++++++---- include/linux/pmem.h | 17 +++++++++++++---- 4 files changed, 36 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h index d8ce3ec816ab..4ef301e78a2b 100644 --- a/arch/x86/include/asm/pmem.h +++ b/arch/x86/include/asm/pmem.h @@ -17,6 +17,7 @@ #include <asm/cacheflush.h> #include <asm/cpufeature.h> #include <asm/special_insns.h> +#include <asm/string.h> #ifdef CONFIG_ARCH_HAS_PMEM_API /** @@ -47,6 +48,21 @@ static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src, BUG(); } +static inline int arch_memcpy_from_pmem(void *dst, const void __pmem *src, + size_t n) +{ + if (IS_ENABLED(CONFIG_MCE_KERNEL_RECOVERY)) { + struct mcsafe_ret ret; + + ret = __mcsafe_copy(dst, (void __force *) src, n); + if (ret.remain) + return -EIO; + return 0; + } + memcpy(dst, (void __force *) src, n); + return 0; +} + /** * arch_wmb_pmem - synchronize writes to persistent memory * diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig index 53c11621d5b1..fe5885d01fd8 100644 --- a/drivers/nvdimm/Kconfig +++ b/drivers/nvdimm/Kconfig @@ -22,6 +22,7 @@ config BLK_DEV_PMEM depends on HAS_IOMEM select ND_BTT if BTT select ND_PFN if NVDIMM_PFN + select MCE_KERNEL_RECOVERY if X86_MCE && X86_64 help Memory ranges for PMEM are described by either an NFIT (NVDIMM Firmware Interface Table, see CONFIG_NFIT_ACPI), a diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 8744235b5be2..d8e14e962327 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -62,6 +62,7 @@ static bool is_bad_pmem(struct badblocks *bb, sector_t sector, unsigned int len) static int pmem_do_bvec(struct block_device *bdev, struct page *page, unsigned int len, unsigned int off, int rw, sector_t sector) { + int rc = 0; void *mem = kmap_atomic(page); struct gendisk *disk = bdev->bd_disk; struct pmem_device *pmem = disk->private_data; @@ -71,7 +72,7 @@ static int pmem_do_bvec(struct block_device *bdev, struct page *page, if (rw == READ) { if (unlikely(is_bad_pmem(disk->bb, sector, len))) return -EIO; - memcpy_from_pmem(mem + off, pmem_addr, len); + rc = memcpy_from_pmem(mem + off, pmem_addr, len); flush_dcache_page(page); } else { flush_dcache_page(page); @@ -79,7 +80,7 @@ static int pmem_do_bvec(struct block_device *bdev, struct page *page, } kunmap_atomic(mem); - return 0; + return rc; } static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio) @@ -237,6 +238,7 @@ static int pmem_rw_bytes(struct nd_namespace_common *ndns, resource_size_t offset, void *buf, size_t size, int rw) { struct pmem_device *pmem = dev_get_drvdata(ndns->claim); + int rc = 0; if (unlikely(offset + size > pmem->size)) { dev_WARN_ONCE(&ndns->dev, 1, "request out of range\n"); @@ -244,13 +246,13 @@ static int pmem_rw_bytes(struct nd_namespace_common *ndns, } if (rw == READ) - memcpy_from_pmem(buf, pmem->virt_addr + offset, size); + rc = memcpy_from_pmem(buf, pmem->virt_addr + offset, size); else { memcpy_to_pmem(pmem->virt_addr + offset, buf, size); wmb_pmem(); } - return 0; + return rc; } static int nd_pfn_init(struct nd_pfn *nd_pfn) diff --git a/include/linux/pmem.h b/include/linux/pmem.h index acfea8ce4a07..0e57a5beab21 100644 --- a/include/linux/pmem.h +++ b/include/linux/pmem.h @@ -42,6 +42,13 @@ static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src, BUG(); } +static inline int arch_memcpy_from_pmem(void *dst, + const void __pmem *src, size_t n) +{ + BUG(); + return 0; +} + static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes, struct iov_iter *i) { @@ -57,12 +64,14 @@ static inline void arch_clear_pmem(void __pmem *addr, size_t size) /* * Architectures that define ARCH_HAS_PMEM_API must provide - * implementations for arch_memcpy_to_pmem(), arch_wmb_pmem(), - * arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem(). + * implementations for arch_memcpy_to_pmem(), arch_memcpy_from_pmem(), + * arch_wmb_pmem(), arch_copy_from_iter_pmem(), arch_clear_pmem() and + * arch_has_wmb_pmem(). */ -static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size) +static inline int memcpy_from_pmem(void *dst, void __pmem const *src, + size_t size) { - memcpy(dst, (void __force const *) src, size); + return arch_memcpy_from_pmem(dst, src, size); } static inline bool arch_has_pmem_api(void)
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