Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932373AbbHNDax (ORCPT ); Thu, 13 Aug 2015 23:30:53 -0400 Received: from mail-io0-f172.google.com ([209.85.223.172]:35997 "EHLO mail-io0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932081AbbHNDav (ORCPT ); Thu, 13 Aug 2015 23:30:51 -0400 MIME-Version: 1.0 In-Reply-To: <20150813143150.GA17183@lst.de> References: <1439363150-8661-1-git-send-email-hch@lst.de> <1439363150-8661-30-git-send-email-hch@lst.de> <20150813143150.GA17183@lst.de> Date: Thu, 13 Aug 2015 20:30:49 -0700 X-Google-Sender-Auth: epu66dX39aESb2z3-1Y3WUDi2xs Message-ID: Subject: Re: [PATCH 29/31] parisc: handle page-less SG entries From: Dan Williams To: Christoph Hellwig Cc: Linus Torvalds , linux-mips , "linux-ia64@vger.kernel.org" , "linux-nvdimm@lists.01.org" , David Howells , sparclinux@vger.kernel.org, Hans-Christian Egtvedt , "linux-arch@vger.kernel.org" , linux-s390 , "the arch/x86 maintainers" , David Woodhouse , =?UTF-8?Q?H=C3=A5vard_Skinnemoen?= , linux-xtensa@linux-xtensa.org, grundler@parisc-linux.org, Miao Steven , Alex Williamson , linux-metag@vger.kernel.org, Jens Axboe , Michal Simek , Parisc List , Vineet Gupta , Linux Kernel Mailing List , linux-alpha@vger.kernel.org, Linux Media Mailing List , ppc-dev Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1290 Lines: 25 On Thu, Aug 13, 2015 at 7:31 AM, Christoph Hellwig wrote: > On Wed, Aug 12, 2015 at 09:01:02AM -0700, Linus Torvalds wrote: >> I'm assuming that anybody who wants to use the page-less >> scatter-gather lists always does so on memory that isn't actually >> virtually mapped at all, or only does so on sane architectures that >> are cache coherent at a physical level, but I'd like that assumption >> *documented* somewhere. > > It's temporarily mapped by kmap-like helpers. That code isn't in > this series. The most recent version of it is here: > > https://git.kernel.org/cgit/linux/kernel/git/djbw/nvdimm.git/commit/?h=pfn&id=de8237c99fdb4352be2193f3a7610e902b9bb2f0 > > note that it's not doing the cache flushing it would have to do yet, but > it's also only enabled for x86 at the moment. For virtually tagged caches I assume we would temporarily map with kmap_atomic_pfn_t(), similar to how drm_clflush_pages() implements powerpc support. However with DAX we could end up with multiple virtual aliases for a page-less pfn. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/