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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 711A9CA9ECF for ; Mon, 4 Nov 2019 18:37:03 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 4D5782084D for ; Mon, 4 Nov 2019 18:37:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="iRIiJb4H" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D5782084D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 17749EEC; Mon, 4 Nov 2019 18:37:02 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id E91D9EC6 for ; Mon, 4 Nov 2019 18:37:00 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 99646A9 for ; Mon, 4 Nov 2019 18:37:00 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 982402084D; Mon, 4 Nov 2019 18:36:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572892620; bh=rI9UdgOktprMFD0/dk/zkRwmYAt4WKteXodRLuUYe3g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iRIiJb4HSMW81NtrCy2YeZDd7heklVx9fWbj/p5yijsTcRuRNChpwHsmixfH32DXy 6Q0vgAbPOQB300DZVgLFEEeKloViv3Yve8PbvfJQrZB4yHkNKHhgoET4uYEk8ZVhrI ethMrdUnoMXe2II1IvQZG9bduv2G3tKVRaVQ/IXU= Date: Mon, 4 Nov 2019 18:36:56 +0000 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH v2 08/10] iommu/io-pgtable-arm: Rationalise TTBRn handling Message-ID: <20191104183655.GH24909@willie-the-truck> References: <74ada0e6c488a2310206a553eb108cc28fd52457.1572024120.git.robin.murphy@arm.com> <5324d888-857a-b07c-439c-4ae4ea3a9784@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, Steven Price X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Mon, Oct 28, 2019 at 06:51:55PM +0000, Robin Murphy wrote: > On 28/10/2019 15:09, Steven Price wrote: > [...] > > > --- a/drivers/iommu/io-pgtable-arm-v7s.c > > > +++ b/drivers/iommu/io-pgtable-arm-v7s.c > > > @@ -822,15 +822,13 @@ static struct io_pgtable *arm_v7s_alloc_pgtable(struct io_pgtable_cfg *cfg, > > > /* Ensure the empty pgd is visible before any actual TTBR write */ > > > wmb(); > > > - /* TTBRs */ > > > - cfg->arm_v7s_cfg.ttbr[0] = virt_to_phys(data->pgd) | > > > - ARM_V7S_TTBR_S | ARM_V7S_TTBR_NOS | > > > - (cfg->coherent_walk ? > > > - (ARM_V7S_TTBR_IRGN_ATTR(ARM_V7S_RGN_WBWA) | > > > - ARM_V7S_TTBR_ORGN_ATTR(ARM_V7S_RGN_WBWA)) : > > > - (ARM_V7S_TTBR_IRGN_ATTR(ARM_V7S_RGN_NC) | > > > - ARM_V7S_TTBR_ORGN_ATTR(ARM_V7S_RGN_NC))); > > > - cfg->arm_v7s_cfg.ttbr[1] = 0; > > > + /* TTBR */ > > > + cfg->arm_v7s_cfg.ttbr = virt_to_phys(data->pgd) | ARM_V7S_TTBR_S | > > > + (cfg->coherent_walk ? (ARM_V7S_TTBR_NOS | > > > + ARM_V7S_TTBR_IRGN_ATTR(ARM_V7S_RGN_WBWA) | > > > + ARM_V7S_TTBR_ORGN_ATTR(ARM_V7S_RGN_WBWA)) : > > > + (ARM_V7S_TTBR_IRGN_ATTR(ARM_V7S_RGN_NC) | > > > + ARM_V7S_TTBR_ORGN_ATTR(ARM_V7S_RGN_NC))); > > > > ARM_V7S_TTBR_NOS seems to have sneaked into the cfg->coherent_walk > > condition here - which you haven't mentioned in the commit log, so it > > doesn't look like it should be in this commit. > > Ah, yes, it's taken a while to remember whether this was something important > that got muddled up in rebasing, but it's actually just trivial cleanup. For > !coherent_walk, the non-cacheable output attribute makes shareable accesses > implicitly outer-shareable, so setting TTBR.NOS for that case actually does > nothing except look misleading. Thus this is essentially just a cosmetic > change included in the reformatting for clarity and consistency with the > LPAE version. I'll call that out in the commit message, thanks for spotting! I vaguely remember a case where you had to mark non-cacheable accesses as outer-shareable explicitly to avoid unpredictable behaviour. Hmm. /me looks at the Arm ARM Ok, it looks like this changed between ARMv7 and ARMv8. The ARMv7 ARM states: | A memory region with a resultant memory type attribute of Normal, and a | resultant cacheability attribute of Inner Non-cacheable, Outer | Non-cacheable, must have a resultant shareability attribute of Outer | Shareable, otherwise shareability is UNPREDICTABLE. Although this only seems to be the case for LPAE! The short descriptor docs are less clear, but I think it might be wise to ensure that non-cacheable mappings are always outer-shareable for consistency. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu