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,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 EF29FC433FE for ; Mon, 20 Sep 2021 10:59:42 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 B0C8E6058D for ; Mon, 20 Sep 2021 10:59:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B0C8E6058D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=v7HiSN9c5UO0yrSVFJmK8j1ZkXzKteKzgmOYKocuG+0=; b=yomUV9jIyooRJE jKno/tItPNoWxJLjDnrfL6clzhvcvqnl+SULY6UyTKkzyQ1UQZSCj3r+0+3BajmN+MC9+XdH2HrZ4 cETwOIFzI9QM1J1FVZwQxMvCBwZAQstLCFMl7f89uBK+XzdDPZzQEOQ1R/V+AnfKihMXrrb59DqiQ dx315f3RoxxyMyztL+/5vzr+rY+5dTwWQ2+7WDsZsQv+aptcDqtIzin5oCsKYi38VGCpp+VQ3YbUT phgOhKYmlz9j2mDWsmpcs/PP5aKBCsdduKP9AHcjCZR/05iFDyTjlx3qq9TUWqfk5hjHCGiwTWUOe RKebzBJjHx5IeTesZB9w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mSGzv-001LdY-Og; Mon, 20 Sep 2021 10:58:07 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mSGzs-001Lcr-2x for linux-arm-kernel@lists.infradead.org; Mon, 20 Sep 2021 10:58:05 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7885B60F3A; Mon, 20 Sep 2021 10:58:01 +0000 (UTC) Date: Mon, 20 Sep 2021 11:57:58 +0100 From: Catalin Marinas To: Mike Rapoport Cc: Christoph Hellwig , David Hildenbrand , Robin Murphy , Alex Bee , Will Deacon , Andrew Morton , Anshuman Khandual , Linux Kernel Mailing List , linux-mm@kvack.org, Linux ARM Subject: Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases) Message-ID: References: <20210824173741.GC623@arm.com> <0908ce39-7e30-91fa-68ef-11620f9596ae@arm.com> <60a11eba-2910-3b5f-ef96-97d4556c1596@redhat.com> <20210825102044.GA3420@arm.com> <20210918051843.GA16104@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210920_035804_192991_005D7DC9 X-CRM114-Status: GOOD ( 21.85 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Sep 18, 2021 at 02:39:49PM +0300, Mike Rapoport wrote: > On Sat, Sep 18, 2021 at 11:37:22AM +0300, Mike Rapoport wrote: > > On Sat, Sep 18, 2021 at 07:18:43AM +0200, Christoph Hellwig wrote: > > > On Sat, Sep 18, 2021 at 12:22:47AM +0300, Mike Rapoport wrote: > > > > I did some digging and it seems that the most "generic" way to check if a > > > > page is in RAM is page_is_ram(). It's not 100% bullet proof as it'll give > > > > false negatives for architectures that do not register "System RAM", but > > > > those are not using dma_map_resource() anyway and, apparently, never would. > > > > > > The downside of page_is_ram is that it looks really expensiv for > > > something done at dma mapping time. > > > > Indeed :( > > But pfn_valid is plain wrong... > > I'll keep digging. > > I did some more archaeology and it that check for pfn_valid() was requested > by arm folks because their MMU may have troubles with alias mappings with > different attributes and so they made the check to use a false assumption > that pfn_valid() == "RAM". > > As this WARN_ON(pfn_valid()) is only present in dma_map_resource() it's > probably safe to drop it entirely. I agree, we should drop it. IIUC dma_map_resource() does not create any kernel mapping to cause problems with attribute aliasing. You'd need a prior devm_ioremap_resource() if you want access to that range from the CPU side. For arm64 at least, the latter ends up with a pfn_is_map_memory() check. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel