From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C622BC3F2D1 for ; Mon, 2 Mar 2020 21:22:29 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7BB6C208C3 for ; Mon, 2 Mar 2020 21:22:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7BB6C208C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=deltatee.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48WY4z0b61zDqf0 for ; Tue, 3 Mar 2020 08:22:27 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=deltatee.com (client-ip=207.54.116.67; helo=ale.deltatee.com; envelope-from=logang@deltatee.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=deltatee.com Received: from ale.deltatee.com (ale.deltatee.com [207.54.116.67]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48WY2r68YwzDqPc for ; Tue, 3 Mar 2020 08:20:34 +1100 (AEDT) Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.92) (envelope-from ) id 1j8sTx-0000TW-UO; Mon, 02 Mar 2020 14:20:10 -0700 To: Dan Williams References: <20200221182503.28317-1-logang@deltatee.com> <20200221182503.28317-8-logang@deltatee.com> From: Logan Gunthorpe Message-ID: <6e2591ad-4605-aba4-c7b8-2345940e91b4@deltatee.com> Date: Mon, 2 Mar 2020 14:20:07 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: jgg@ziepe.ca, ebadger@gigaio.com, peterz@infradead.org, luto@kernel.org, dave.hansen@linux.intel.com, bp@alien8.de, mingo@redhat.com, tglx@linutronix.de, benh@kernel.crashing.org, will@kernel.org, catalin.marinas@arm.com, hch@lst.de, akpm@linux-foundation.org, david@redhat.com, mhocko@kernel.org, linux-mm@kvack.org, platform-driver-x86@vger.kernel.org, linux-sh@vger.kernel.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-ia64@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, dan.j.williams@intel.com X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v3 7/7] mm/memremap: Set caching mode for PCI P2PDMA memory to WC X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, Linux-sh , Peter Zijlstra , Catalin Marinas , Dave Hansen , platform-driver-x86@vger.kernel.org, Linux MM , Will Deacon , Christoph Hellwig , linux-s390 , David Hildenbrand , Jason Gunthorpe , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Thomas Gleixner , Michal Hocko , Linux ARM , Eric Badger , Linux Kernel Mailing List , Andrew Morton , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 2020-02-29 3:47 p.m., Dan Williams wrote: > On Fri, Feb 21, 2020 at 10:25 AM Logan Gunthorpe wrote: >> >> PCI BAR IO memory should never be mapped as WB, however prior to this >> the PAT bits were set WB and it was typically overridden by MTRR >> registers set by the firmware. >> >> Set PCI P2PDMA memory to be WC (writecombining) as the only current >> user (the NVMe CMB) was originally mapped WC before the P2PDMA code >> replaced the mapping with devm_memremap_pages(). > > Will the change to UC regress this existing use case? I don't think so. They've been essentially mapped UC for a long time now (since the P2PDMA patch set was merged) and nobody has complained.