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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 8F962C3A589 for ; Tue, 20 Aug 2019 15:26:02 +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 640F122CE3 for ; Tue, 20 Aug 2019 15:26:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="CbHFe3EM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 640F122CE3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mVBFSGA+Dr2zDYgOs/s24zMi9qHeGih8DVBaoxaOF/I=; b=CbHFe3EMvGyycGVKNB2R/5niO OGB/61T/AJp7rODONoWi6qgtOrXh/89TMfZK/cE6f0KB/MLAXDvCzWDldPGVyZePHRrIt3VcqH/VI KcygY37uY2pdUYYysjQ0Fh2G804wY/ORp735D9x0FIlrZGPJdBmztjhzv5/r3Pc3VlT/B5676tLgx wenUvgK9bxq4fLprwpLbge669GMzEZkPAwhz+tolMaAvz/nRP8boqIzZqIRhblGwcytrBoMRLvO+B zBn+cK6zgls5HtLsyb5nyyWjzdQtjreyC37xxYCpTPVV4l1EwlsCu0uXxpIzbZCOlZTZ/PLagRpx7 BquzTi4iA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i061J-0005Cn-NB; Tue, 20 Aug 2019 15:26:01 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i061G-0005CH-Tk for linux-arm-kernel@lists.infradead.org; Tue, 20 Aug 2019 15:26:00 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4DB32360; Tue, 20 Aug 2019 08:25:58 -0700 (PDT) Received: from [10.1.197.57] (e110467-lin.cambridge.arm.com [10.1.197.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 807463F246; Tue, 20 Aug 2019 08:25:57 -0700 (PDT) Subject: Re: [PATCH 3/4] iommu/io-pgtable-arm: Rationalise TCR handling To: Will Deacon References: <78df4f8e2510e88f3ded59eb385f79b4442ed4f2.1566238530.git.robin.murphy@arm.com> <20190820103115.o7neehdethf7sbqi@willie-the-truck> From: Robin Murphy Message-ID: <48ca6945-de73-116a-3230-84862ca9e60b@arm.com> Date: Tue, 20 Aug 2019 16:25:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190820103115.o7neehdethf7sbqi@willie-the-truck> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190820_082558_997920_28F41516 X-CRM114-Status: GOOD ( 19.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: robdclark@gmail.com, joro@8bytes.org, jcrouse@codeaurora.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 20/08/2019 11:31, Will Deacon wrote: > On Mon, Aug 19, 2019 at 07:19:30PM +0100, Robin Murphy wrote: >> Although it's conceptually nice for the io_pgtable_cfg to provide a >> standard VMSA TCR value, the reality is that no VMSA-compliant IOMMU >> looks exactly like an Arm CPU, and they all have various other TCR >> controls which io-pgtable can't be expected to understand. Thus since >> there is an expectation that drivers will have to add to the given TCR >> value anyway, let's strip it down to just the essentials that are >> directly relevant to io-pgatble's inner workings - namely the address >> sizes, walk attributes, and where appropriate, format selection. >> >> Signed-off-by: Robin Murphy >> --- >> drivers/iommu/arm-smmu-v3.c | 7 +------ >> drivers/iommu/arm-smmu.c | 1 + >> drivers/iommu/arm-smmu.h | 2 ++ >> drivers/iommu/io-pgtable-arm-v7s.c | 6 ++---- >> drivers/iommu/io-pgtable-arm.c | 4 ---- >> drivers/iommu/qcom_iommu.c | 2 +- >> 6 files changed, 7 insertions(+), 15 deletions(-) > > Hmm, so I'm a bit nervous about this one since I think we really should > be providing a TCR with EPD1 set if we're only giving you TTBR0. Relying > on the driver to do this worries me. See my comments on the next patch. The whole idea is that we already know we can't provide a *complete* TCR value (not least because anything above bit 31 is the wild west), thus there's really no point in io-pgtable trying to provide anything other than the parts it definitely controls. It makes sense to provide this partial TCR value "as if" for TTBR0, since that's the most common case, but ultimately io-pgatble doesn't know (or need to) which TTBR the caller intends to actually use for this table. Even if the caller *is* allocating it for TTBR0, io-pgtable doesn't know that they haven't got something live in TTBR1 already, so it still wouldn't be in a position to make the EPD1 call either way. Ultimately, it's the IOMMU drivers who decide what they put in which TTBR, so it's the IOMMU drivers which have to take responsibility for EPD*. Sure you can worry about it, but you can equally worry about them them misprogramming the ASID or anything else... Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel