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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 D01B4C43331 for ; Tue, 12 Nov 2019 22:02:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A20472196E for ; Tue, 12 Nov 2019 22:02:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K16IxrZq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726923AbfKLWCQ (ORCPT ); Tue, 12 Nov 2019 17:02:16 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:51124 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726896AbfKLWCP (ORCPT ); Tue, 12 Nov 2019 17:02:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=7jAEbZsBzv3PFISvUcPFIFd7joU8uP8zZrxP8zk/r9M=; b=K16IxrZqUhqYgrANYfZo7ZnoD feYnXP9G733dvNL6/NsO3XGUkXqkNGRgGIRqKsPy38+Ued5nKS4GIFDNZhC5X7kAhq241K5uLSzHK cgqa7pAgkjuTVkfuyHdgHl3AawqxRhEQX5mFdKogL4n85ZBuXblzmmuSVRmEYCaReEhQTYtkVqdh/ Ewg8hdV2JRyXaUqsBSBGiEGssfnGsfoTfpjqrwty7p9wEM50oTuSkQY1OZAoQUW87W5Xy7Ftm7fMf 3W7ntvKrQMgeDFRIyqugl/z8IxQ0C895lbV5qQ3zgU+6Y7kbuGXRR3YjWZ73FpjOpGuU/AxrFAImg NseFvGxSA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iUeEm-0001EA-GF; Tue, 12 Nov 2019 22:02:12 +0000 Date: Tue, 12 Nov 2019 14:02:12 -0800 From: Matthew Wilcox To: Dan Williams Cc: Bharat Kumar Gogada , "linux-nvdimm@lists.01.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "viro@zeniv.linux.org.uk" , "jack@suse.cz" Subject: Re: DAX filesystem support on ARMv8 Message-ID: <20191112220212.GC7934@bombadil.infradead.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Nov 12, 2019 at 09:15:18AM -0800, Dan Williams wrote: > On Mon, Nov 11, 2019 at 6:12 PM Bharat Kumar Gogada wrote: > > > > Hi All, > > > > As per Documentation/filesystems/dax.txt > > > > The DAX code does not work correctly on architectures which have virtually > > mapped caches such as ARM, MIPS and SPARC. > > > > Can anyone please shed light on dax filesystem issue w.r.t ARM architecture ? > > The concern is VIVT caches since the kernel will want to flush pmem > addresses with different virtual addresses than what userspace is > using. As far as I know, ARMv8 has VIPT caches, so should not have an > issue. Willy initially wrote those restrictions, but I am assuming > that the concern was managing the caches in the presence of virtual > aliases. The kernel will also access data at different virtual addresses from userspace. So VIVT CPUs will be mmap/read/write incoherent, as well as being flush incoherent.