linux-kernel - Re: [PATCH v3] x86, pmem: use memcpy_mcsafe() for memcpy_from

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Date:	Mon, 28 Mar 2016 17:31:20 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Cc:	Tony Luck <tony.luck@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v3] x86, pmem: use memcpy_mcsafe() for memcpy_from_pmem()

On Mon, Mar 28, 2016 at 5:28 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> Update the definition of memcpy_from_pmem() to return 0 or a negative
> error code.  Implement x86/arch_memcpy_from_pmem() with memcpy_mcsafe().
>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  arch/x86/include/asm/pmem.h |    9 +++++++++
>  drivers/nvdimm/pmem.c       |    4 ++--
>  include/linux/pmem.h        |   21 +++++++++++++++------
>  3 files changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
> index bf8b35d2035a..fbc5e92e1ecc 100644
> --- a/arch/x86/include/asm/pmem.h
> +++ b/arch/x86/include/asm/pmem.h
> @@ -47,6 +47,15 @@ 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 (static_cpu_has(X86_FEATURE_MCE_RECOVERY))
> +               return memcpy_mcsafe(dst, (void __force *) src, n);
> +       memcpy(dst, (void __force *) src, n);
> +       return 0;
> +}
> +
>  /**
>   * arch_wmb_pmem - synchronize writes to persistent memory
>   *
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index ca5721c306bb..cc31c6f1f88e 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -99,7 +99,7 @@ static int pmem_do_bvec(struct pmem_device *pmem, struct page *page,
>                 if (unlikely(bad_pmem))
>                         rc = -EIO;
>                 else {
> -                       memcpy_from_pmem(mem + off, pmem_addr, len);
> +                       rc = memcpy_from_pmem(mem + off, pmem_addr, len);
>                         flush_dcache_page(page);
>                 }
>         } else {
> @@ -295,7 +295,7 @@ static int pmem_rw_bytes(struct nd_namespace_common *ndns,
>
>                 if (unlikely(is_bad_pmem(&pmem->bb, offset / 512, sz_align)))
>                         return -EIO;
> -               memcpy_from_pmem(buf, pmem->virt_addr + offset, size);
> +               return memcpy_from_pmem(buf, pmem->virt_addr + offset, size);
>         } else {
>                 memcpy_to_pmem(pmem->virt_addr + offset, buf, size);
>                 wmb_pmem();
> diff --git a/include/linux/pmem.h b/include/linux/pmem.h
> index 3ec5309e29f3..cc948191a653 100644
> --- a/include/linux/pmem.h
> +++ b/include/linux/pmem.h
> @@ -42,6 +42,12 @@ 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();
> +}

Note, the change in v3 was the addition of this stub to fix a build
error on !CONFIG_ARCH_HAS_PMEM_API archs.