Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422961AbbENWjx (ORCPT ); Thu, 14 May 2015 18:39:53 -0400 Received: from g1t5425.austin.hp.com ([15.216.225.55]:54372 "EHLO g1t5425.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161156AbbENWju (ORCPT ); Thu, 14 May 2015 18:39:50 -0400 Message-ID: <1431642030.22510.8.camel@misato.fc.hp.com> Subject: Re: [PATCH v9 10/10] drivers/block/pmem: Map NVDIMM with ioremap_wt() From: Toshi Kani To: Dan Williams Cc: "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Andrew Morton , Arnd Bergmann , jgross@suse.com, Konrad Rzeszutek Wilk , "linux-nvdimm@lists.01.org" , mcgrof@suse.com, X86 ML , "linux-kernel@vger.kernel.org" , stefan.bader@canonical.com, Andy Lutomirski , linux-mm@kvack.org, hmh@hmh.eng.br, Christoph Hellwig , Matthew Wilcox Date: Thu, 14 May 2015 16:20:30 -0600 In-Reply-To: References: <1431551151-19124-1-git-send-email-toshi.kani@hp.com> <1431551151-19124-11-git-send-email-toshi.kani@hp.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4 (3.10.4-4.fc20) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1350 Lines: 29 On Thu, 2015-05-14 at 14:52 -0700, Dan Williams wrote: > On Wed, May 13, 2015 at 2:05 PM, Toshi Kani wrote: > > The pmem driver maps NVDIMM with ioremap_nocache() as we cannot > > write back the contents of the CPU caches in case of a crash. > > > > This patch changes to use ioremap_wt(), which provides uncached > > writes but cached reads, for improving read performance. > > I'm thinking that for the libnd integration we don't want the pmem > driver hard coding the cache-policy decision. This is something that > should be specified to nd_pmem_region_create(). Especially > considering that platform firmware tables (NFIT) may specify the cache > policy for the range. As Matthew Wilcox mentioned offline we also > must match the DAX-to-mmap cache policy with the policy for the driver > mapping for architectures that are not capable of multiple mappings > of the same physical address with different policies. Agreed. I believe this hardcoded ioremap is temporary (either UC- or WT), and we need to allow NFIT or user to specify a map type, such as WB. Thanks, -Toshi -- 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/