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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 ACF0DC43460 for ; Wed, 5 May 2021 18:02:41 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 07E8F613AA for ; Wed, 5 May 2021 18:02:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07E8F613AA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 833364B504; Wed, 5 May 2021 14:02:40 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9YazY6PzOMru; Wed, 5 May 2021 14:02:39 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8B63F4B50A; Wed, 5 May 2021 14:02:39 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E722F4B510 for ; Wed, 5 May 2021 14:02:37 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id bfCvyx-mejYr for ; Wed, 5 May 2021 14:02:36 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id CB9D54B508 for ; Wed, 5 May 2021 14:02:36 -0400 (EDT) Received: by mail.kernel.org (Postfix) with ESMTPSA id BB46861176; Wed, 5 May 2021 18:02:33 +0000 (UTC) Date: Wed, 5 May 2021 19:02:31 +0100 From: Catalin Marinas To: Will Deacon Subject: Re: [RFC 1/2] vfio/pci: keep the prefetchable attribute of a BAR region in VMA Message-ID: <20210505180228.GA3874@arm.com> References: <878s4zokll.wl-maz@kernel.org> <87eeeqvm1d.wl-maz@kernel.org> <87bl9sunnw.wl-maz@kernel.org> <20210503084432.75e0126d@x1.home.shazbot.org> <20210504083005.GA12290@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210504083005.GA12290@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , Marc Zyngier , Shanker Donthineni , Vikram Sethi , Alex Williamson , Jason Sequeira , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" , Mark Kettenis X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tue, May 04, 2021 at 09:30:05AM +0100, Will Deacon wrote: > On Mon, May 03, 2021 at 10:03:59PM +0000, Vikram Sethi wrote: > > Will/Catalin, perhaps you could explain your thought process on why you chose > > Normal NC for ioremap_wc on the armv8 linux port instead of Device GRE or other > > Device Gxx. > > I think a combination of: compatibility with 32-bit Arm, the need to > support unaligned accesses and the potential for higher performance. IIRC the _wc suffix also matches the pgprot_writecombine() used by some drivers to map a video framebuffer into user space. Accesses to the framebuffer are not guaranteed to be aligned (memset/memcpy don't ensure alignment on arm64 and the user doesn't have a memset_io or memcpy_toio). > Furthermore, ioremap() already gives you a Device memory type, and we're > tight on MAIR space. We have MT_DEVICE_GRE currently reserved though no in-kernel user, we might as well remove it. -- Catalin _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm