From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f54.google.com (mail-wg0-f54.google.com [74.125.82.54]) by kanga.kvack.org (Postfix) with ESMTP id 6E5486B006E for ; Mon, 22 Jun 2015 12:17:57 -0400 (EDT) Received: by wgbhy7 with SMTP id hy7so145876969wgb.2 for ; Mon, 22 Jun 2015 09:17:57 -0700 (PDT) Received: from newverein.lst.de (verein.lst.de. [213.95.11.211]) by mx.google.com with ESMTPS id d13si35832694wjs.32.2015.06.22.09.17.55 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jun 2015 09:17:55 -0700 (PDT) Date: Mon, 22 Jun 2015 18:17:54 +0200 From: Christoph Hellwig Subject: Re: [PATCH v5 6/6] arch, x86: pmem api for ensuring durability of persistent memory updates Message-ID: <20150622161754.GC8240@lst.de> References: <20150622081028.35954.89885.stgit@dwillia2-desk3.jf.intel.com> <20150622082449.35954.91411.stgit@dwillia2-desk3.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150622082449.35954.91411.stgit@dwillia2-desk3.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: arnd@arndb.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, tglx@linutronix.de, ross.zwisler@linux.intel.com, akpm@linux-foundation.org, jgross@suse.com, x86@kernel.org, toshi.kani@hp.com, linux-nvdimm@lists.01.org, benh@kernel.crashing.org, mcgrof@suse.com, konrad.wilk@oracle.com, linux-kernel@vger.kernel.org, stefan.bader@canonical.com, luto@amacapital.net, linux-mm@kvack.org, geert@linux-m68k.org, ralf@linux-mips.org, hmh@hmh.eng.br, mpe@ellerman.id.au, tj@kernel.org, paulus@samba.org, Richard Weinberger > +#ifdef ARCH_HAS_NOCACHE_UACCESS Seems like this is always define for x86 anyway? > +/** > + * arch_memcpy_to_pmem - copy data to persistent memory > + * @dst: destination buffer for the copy > + * @src: source buffer for the copy > + * @n: length of the copy in bytes > + * > + * Copy data to persistent memory media via non-temporal stores so that > + * a subsequent arch_wmb_pmem() can flush cpu and memory controller > + * write buffers to guarantee durability. > + */ static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src, size_t n) Too long line. Also why not simply arch_copy_{from,to}_pmem? > +#else /* ARCH_HAS_NOCACHE_UACCESS i.e. ARCH=um */ Oh, UM. I'd rather see UM fixed to provide these. Richard, any chance you could look into it? > diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h > index 97ae3b748d9e..0d3e43f679aa 100644 > --- a/arch/x86/include/asm/io.h > +++ b/arch/x86/include/asm/io.h > @@ -249,6 +249,12 @@ static inline void flush_write_buffers(void) > #endif > } > > +static inline void __pmem *arch_memremap_pmem(resource_size_t offset, > + unsigned long size) > +{ > + return (void __force __pmem *) ioremap_cache(offset, size); > +} Now with my ioremap_flags proposal we'd just add an IOREMAP_PMEM flag, which architectures could implement (usually as no-op), and move the cast into memremap_pmem. > + * These defaults seek to offer decent performance and minimize the > + * window between i/o completion and writes being durable on media. > + * However, it is undefined / architecture specific whether > + * default_memremap_pmem + default_memcpy_to_pmem is sufficient for > + * making data durable relative to i/o completion. > + */ > +static void default_memcpy_to_pmem(void __pmem *dst, const void *src, size_t size) > +{ > + memcpy((void __force *) dst, src, size); > +} This should really be in asm-generic (or at least your linux/pmem.h for now). > +static void __pmem *default_memremap_pmem(resource_size_t offset, unsigned long size) > +{ > + return (void __pmem *)memremap_wt(offset, size); > +} And this as well, unless we can get rid of it entirely with ioremap_flags(). > if (rw == READ) { > - memcpy(mem + off, pmem->virt_addr + pmem_off, len); > + memcpy_from_pmem(mem + off, pmem_addr, len); > flush_dcache_page(page); > } else { > flush_dcache_page(page); > - memcpy(pmem->virt_addr + pmem_off, mem + off, len); > + if (arch_has_pmem_api()) > + memcpy_to_pmem(pmem_addr, mem + off, len); > + else > + default_memcpy_to_pmem(pmem_addr, mem + off, len); So memcpy_from_pmem hides the different but memcpy_to_pmem doesn't? That seems pretty awkward. Please move the check into the helper. > + if (rw && arch_has_pmem_api()) > + wmb_pmem(); And here again make sure wmb_pmem is always available and a no-op if not supported. > + if (arch_has_pmem_api()) > + pmem->virt_addr = memremap_pmem(pmem->phys_addr, pmem->size); > + else > + pmem->virt_addr = default_memremap_pmem(pmem->phys_addr, > + pmem->size); All of this should be hidden in memremap_pmem. -- 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: email@kvack.org