From: Andy Lutomirski <luto@amacapital.net> To: Dan Williams <dan.j.williams@intel.com> Cc: Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ross Zwisler <ross.zwisler@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Juergen Gross <jgross@suse.com>, X86 ML <x86@kernel.org>, Toshi Kani <toshi.kani@hp.com>, linux-nvdimm <linux-nvdimm@lists.01.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Luis Rodriguez <mcgrof@suse.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Stefan Bader <stefan.bader@canonical.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Geert Uytterhoeven <geert@linux-m68k.org>, Ralf Baechle <ralf@linux-mips.org>, Henrique de Moraes Holschuh <hmh@hmh.eng.br>, Michael Ellerman <mpe@ellerman.id.au>, Tejun Heo <tj@kernel.org>, Paul Mackerras <paulus@samba.org>, Christoph Hellwig <hch@lst.de> Subject: Re: [PATCH v4 6/6] arch, x86: pmem api for ensuring durability of persistent memory updates Date: Wed, 17 Jun 2015 08:07:38 -0700 [thread overview] Message-ID: <CALCETrXXYyjKHi1ajR6aescmjSo5eds=5g_byWpzBRbBNdsgRQ@mail.gmail.com> (raw) In-Reply-To: <20150611211947.10271.80768.stgit@dwillia2-desk3.amr.corp.intel.com> On Thu, Jun 11, 2015 at 2:19 PM, Dan Williams <dan.j.williams@intel.com> wrote: > From: Ross Zwisler <ross.zwisler@linux.intel.com> > > Based on an original patch by Ross Zwisler [1]. > > Writes to persistent memory have the potential to be posted to cpu > cache, cpu write buffers, and platform write buffers (memory controller) > before being committed to persistent media. Provide apis, > memcpy_to_pmem(), sync_pmem(), and memremap_pmem(), to write data to > pmem and assert that it is durable in PMEM (a persistent linear address > range). A '__pmem' attribute is added so sparse can track proper usage > of pointers to pmem. > > [1]: https://lists.01.org/pipermail/linux-nvdimm/2015-May/000932.html > > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> > [djbw: various reworks] > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- > arch/x86/Kconfig | 1 > arch/x86/include/asm/cacheflush.h | 36 +++++++++++++ > arch/x86/include/asm/io.h | 6 ++ > drivers/block/pmem.c | 75 +++++++++++++++++++++++++-- > include/linux/compiler.h | 2 + > include/linux/pmem.h | 102 +++++++++++++++++++++++++++++++++++++ > lib/Kconfig | 3 + > 7 files changed, 218 insertions(+), 7 deletions(-) > create mode 100644 include/linux/pmem.h > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index f16caf7eac27..5dfb8f31ac48 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -28,6 +28,7 @@ config X86 > select ARCH_HAS_FAST_MULTIPLIER > select ARCH_HAS_GCOV_PROFILE_ALL > select ARCH_HAS_MEMREMAP > + select ARCH_HAS_PMEM_API > select ARCH_HAS_SG_CHAIN > select ARCH_HAVE_NMI_SAFE_CMPXCHG > select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI > diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h > index b6f7457d12e4..4d896487382c 100644 > --- a/arch/x86/include/asm/cacheflush.h > +++ b/arch/x86/include/asm/cacheflush.h > @@ -4,6 +4,7 @@ > /* Caches aren't brain-dead on the intel. */ > #include <asm-generic/cacheflush.h> > #include <asm/special_insns.h> > +#include <asm/uaccess.h> > > /* > * The set_memory_* API can be used to change various attributes of a virtual > @@ -108,4 +109,39 @@ static inline int rodata_test(void) > } > #endif > > +#ifdef ARCH_HAS_NOCACHE_UACCESS > +static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src, size_t n) > +{ > + /* > + * We are copying between two kernel buffers, if > + * __copy_from_user_inatomic_nocache() returns an error (page > + * fault) we would have already taken an unhandled fault before > + * the BUG_ON. The BUG_ON is simply here to satisfy > + * __must_check and allow reuse of the common non-temporal store > + * implementation for memcpy_to_pmem(). > + */ > + BUG_ON(__copy_from_user_inatomic_nocache((void __force *) dst, > + (void __user *) src, n)); Ick. If we take a fault, we will lose the debugging information we would otherwise have gotten unless we get lucky and get a usable CR2 value in the oops. > +} > + > +static inline void arch_sync_pmem(void) > +{ > + wmb(); > + pcommit_sfence(); > +} This function is non-intuitive to me. It's really "arch-specific sync pmem after one or more copies using arch_memcpy_to_pmem". If normal stores or memcpy to non-WC memory is used instead, then it's insufficient if the memory is WB and it's unnecessarily slow if the memory is WT or UC (the first sfence isn't needed). I would change the name and add documentation. I'd also add a comment about the wmb() being an SFENCE to flush pending non-temporal writes. --Andy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
WARNING: multiple messages have this Message-ID (diff)
From: Andy Lutomirski <luto@amacapital.net> To: Dan Williams <dan.j.williams@intel.com> Cc: Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ross Zwisler <ross.zwisler@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Juergen Gross <jgross@suse.com>, X86 ML <x86@kernel.org>, Toshi Kani <toshi.kani@hp.com>, linux-nvdimm <linux-nvdimm@ml01.01.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Luis Rodriguez <mcgrof@suse.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Stefan Bader <stefan.bader@canonical.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Geert Uytterhoeven <geert@linux-m68k.org>, Ralf Baechle <ralf@linux-mips.org>, Henrique de Moraes Holschuh <hmh@hmh.eng.br>, Michael Ellerman <mpe@ellerman.id.au>, Tejun Heo <tj@kernel.org>, Paul Mackerras <paulus@samba.org>, Christoph Hellwig <hch@lst.de> Subject: Re: [PATCH v4 6/6] arch, x86: pmem api for ensuring durability of persistent memory updates Date: Wed, 17 Jun 2015 08:07:38 -0700 [thread overview] Message-ID: <CALCETrXXYyjKHi1ajR6aescmjSo5eds=5g_byWpzBRbBNdsgRQ@mail.gmail.com> (raw) In-Reply-To: <20150611211947.10271.80768.stgit@dwillia2-desk3.amr.corp.intel.com> On Thu, Jun 11, 2015 at 2:19 PM, Dan Williams <dan.j.williams@intel.com> wrote: > From: Ross Zwisler <ross.zwisler@linux.intel.com> > > Based on an original patch by Ross Zwisler [1]. > > Writes to persistent memory have the potential to be posted to cpu > cache, cpu write buffers, and platform write buffers (memory controller) > before being committed to persistent media. Provide apis, > memcpy_to_pmem(), sync_pmem(), and memremap_pmem(), to write data to > pmem and assert that it is durable in PMEM (a persistent linear address > range). A '__pmem' attribute is added so sparse can track proper usage > of pointers to pmem. > > [1]: https://lists.01.org/pipermail/linux-nvdimm/2015-May/000932.html > > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> > [djbw: various reworks] > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- > arch/x86/Kconfig | 1 > arch/x86/include/asm/cacheflush.h | 36 +++++++++++++ > arch/x86/include/asm/io.h | 6 ++ > drivers/block/pmem.c | 75 +++++++++++++++++++++++++-- > include/linux/compiler.h | 2 + > include/linux/pmem.h | 102 +++++++++++++++++++++++++++++++++++++ > lib/Kconfig | 3 + > 7 files changed, 218 insertions(+), 7 deletions(-) > create mode 100644 include/linux/pmem.h > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index f16caf7eac27..5dfb8f31ac48 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -28,6 +28,7 @@ config X86 > select ARCH_HAS_FAST_MULTIPLIER > select ARCH_HAS_GCOV_PROFILE_ALL > select ARCH_HAS_MEMREMAP > + select ARCH_HAS_PMEM_API > select ARCH_HAS_SG_CHAIN > select ARCH_HAVE_NMI_SAFE_CMPXCHG > select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI > diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h > index b6f7457d12e4..4d896487382c 100644 > --- a/arch/x86/include/asm/cacheflush.h > +++ b/arch/x86/include/asm/cacheflush.h > @@ -4,6 +4,7 @@ > /* Caches aren't brain-dead on the intel. */ > #include <asm-generic/cacheflush.h> > #include <asm/special_insns.h> > +#include <asm/uaccess.h> > > /* > * The set_memory_* API can be used to change various attributes of a virtual > @@ -108,4 +109,39 @@ static inline int rodata_test(void) > } > #endif > > +#ifdef ARCH_HAS_NOCACHE_UACCESS > +static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src, size_t n) > +{ > + /* > + * We are copying between two kernel buffers, if > + * __copy_from_user_inatomic_nocache() returns an error (page > + * fault) we would have already taken an unhandled fault before > + * the BUG_ON. The BUG_ON is simply here to satisfy > + * __must_check and allow reuse of the common non-temporal store > + * implementation for memcpy_to_pmem(). > + */ > + BUG_ON(__copy_from_user_inatomic_nocache((void __force *) dst, > + (void __user *) src, n)); Ick. If we take a fault, we will lose the debugging information we would otherwise have gotten unless we get lucky and get a usable CR2 value in the oops. > +} > + > +static inline void arch_sync_pmem(void) > +{ > + wmb(); > + pcommit_sfence(); > +} This function is non-intuitive to me. It's really "arch-specific sync pmem after one or more copies using arch_memcpy_to_pmem". If normal stores or memcpy to non-WC memory is used instead, then it's insufficient if the memory is WB and it's unnecessarily slow if the memory is WT or UC (the first sfence isn't needed). I would change the name and add documentation. I'd also add a comment about the wmb() being an SFENCE to flush pending non-temporal writes. --Andy
next prev parent reply other threads:[~2015-06-17 15:07 UTC|newest] Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-06-11 21:19 [-tip PATCH v4 0/6] pmem api, generic ioremap_cache, and memremap Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-11 21:19 ` [PATCH v4 1/6] arch: unify ioremap prototypes and macro aliases Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-17 11:14 ` Christoph Hellwig 2015-06-17 11:14 ` Christoph Hellwig 2015-06-17 17:35 ` Toshi Kani 2015-06-17 17:35 ` Toshi Kani 2015-06-11 21:19 ` [PATCH v4 2/6] cleanup IORESOURCE_CACHEABLE vs ioremap() Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-11 21:19 ` [PATCH v4 3/6] arch/*/asm/io.h: add ioremap_cache() to all architectures Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-17 11:27 ` Christoph Hellwig 2015-06-17 11:27 ` Christoph Hellwig 2015-06-11 21:19 ` [PATCH v4 4/6] devm: fix ioremap_cache() usage Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-11 21:19 ` [PATCH v4 5/6] arch: introduce memremap_cache() and memremap_wt() Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-19 21:28 ` Toshi Kani 2015-06-19 21:28 ` Toshi Kani 2015-06-11 21:19 ` [PATCH v4 6/6] arch, x86: pmem api for ensuring durability of persistent memory updates Dan Williams 2015-06-11 21:19 ` Dan Williams 2015-06-17 11:31 ` Christoph Hellwig 2015-06-17 11:31 ` Christoph Hellwig 2015-06-17 14:54 ` Dan Williams 2015-06-17 14:54 ` Dan Williams 2015-06-17 15:08 ` Andy Lutomirski 2015-06-17 15:08 ` Andy Lutomirski 2015-06-17 15:07 ` Andy Lutomirski [this message] 2015-06-17 15:07 ` Andy Lutomirski 2015-06-17 15:15 ` Thomas Gleixner 2015-06-17 15:15 ` Thomas Gleixner
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