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=-8.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,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 135A1C433DF for ; Tue, 13 Oct 2020 13:15:23 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 8E1A122CAD for ; Tue, 13 Oct 2020 13:15:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="EGQJjfNN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E1A122CAD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject: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=QZbeT11ANwgLSBXNkod/7dZ5EA4Dix1z01cV0UyVNzI=; b=EGQJjfNNO/EEkZNw0Gwuekb2P qeOFmKmMQkvLyy6crpZQXtXQ1b65DDNI0SenbQHmuGjXPh5yvViNbNufqsEGY/hcblZ051sbjFTX4 fDiJCapmv5Cf9N/wHWRVTFsMewRD8r3ob3pYpGjBUJGFZ/zWQGw1MAGjEkX97KthUmYcP2iogvyTs j1VCT0ZAd/DJSkbUMS1wt/sLxXpGVOp2ilWV/PrFh+ansAlM4xHNnuZuMyOxv0s9siDOv5Xv6NoGi wdl0vB3hUOvh1e10Wlt7OzTCvzIYKK08xvxIkjCgh4snnzFk21UskTeQDBy9V/g6aZTv1YY6cyxQ6 lH3Aw26kA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSK7q-0003iz-Nx; Tue, 13 Oct 2020 13:13:58 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSK7n-0003i6-Jx for linux-arm-kernel@lists.infradead.org; Tue, 13 Oct 2020 13:13:56 +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 799EE1FB; Tue, 13 Oct 2020 06:13:53 -0700 (PDT) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C7B6F3F719; Tue, 13 Oct 2020 06:13:51 -0700 (PDT) Date: Tue, 13 Oct 2020 14:13:46 +0100 From: Lorenzo Pieralisi To: Ard Biesheuvel Subject: Re: [PATCH] arm64: mm: set ZONE_DMA size based on early IORT scan Message-ID: <20201013131346.GA20925@e121166-lin.cambridge.arm.com> References: <20201010093153.30177-1-ardb@kernel.org> <20201013110929.GB20319@e121166-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201013_091355_770724_25539269 X-CRM114-Status: GOOD ( 39.49 ) 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: Anshuman Khandual , Catalin Marinas , Sudeep Holla , Robin Murphy , Jeremy Linton , ACPI Devel Maling List , Rob Herring , Linux ARM , Hanjun Guo , Will Deacon , Christoph Hellwig , Nicolas Saenz Julienne 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 Tue, Oct 13, 2020 at 01:22:32PM +0200, Ard Biesheuvel wrote: [...] > > > diff --git a/Documentation/arm64/arm-acpi.rst b/Documentation/arm64/arm-acpi.rst > > > index 47ecb9930dde..947f5b5c45ef 100644 > > > --- a/Documentation/arm64/arm-acpi.rst > > > +++ b/Documentation/arm64/arm-acpi.rst > > > @@ -205,6 +205,13 @@ devices available. This list of tables is not meant to be all inclusive; > > > in some environments other tables may be needed (e.g., any of the APEI > > > tables from section 18) to support specific functionality. > > > > > > +It is assumed that all DMA capable devices in the system are able to > > > +access the lowest 4 GB of system memory. If this is not the case, an > > > +IORT describing those limitations is mandatory, even if an IORT is not > > > +otherwise necessary to describe the I/O topology, and regardless of > > > +whether _DMA methods are used to describe the DMA limitations more > > > +precisely. Once the system has booted, _DMA methods will take precedence > > > +over DMA addressing limits described in the IORT. > > > > If this is a boot requirement it must be in ARM's official documentation, > > first, not the kernel one. > > > > I understand this is an urgent (well - no comments on why bootstrapping > > ACPI on Raspberry PI4 is causing all this fuss, honestly) fix but that's > > not a reason to rush through these guidelines. > > > > I would not add this paragraph to arm-acpi.rst, yet. > > > > Which documentation? ACPI compliance by itself is not sufficient for a > system to be able to boot Linux/arm64, which is why we documented the > requirements for ACPI boot on Linux/arm64 in this file. I don't think > we need endorsement from ARM to decide that odd platforms like this > need to abide by some additional rules if they want to boot in ACPI > mode. I think we do - if we don't we should not add this documentation either. ACPI on ARM64 software stack is based on standardized HW requirements. The sheer fact that we need to work around a HW deficiency shows that either this platform should have never been booted with ACPI or the _HW_ design guidelines (BSA) are not tight enough. Please note that as you may have understood I asked if we can implement a workaround in IORT because that's information that must be there regardless (and an OEM ID match in arch code - though pragmatic - defeats the whole purpose), I don't think we should tell Linux kernel developers how firmware must be written to work around blatantly non-compliant systems. Thanks, Lorenzo > > > ACPI Detection > > > -------------- > > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > > index f0599ae73b8d..829fa63c3d72 100644 > > > --- a/arch/arm64/mm/init.c > > > +++ b/arch/arm64/mm/init.c > > > @@ -191,6 +191,14 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > > > unsigned long max_zone_pfns[MAX_NR_ZONES] = {0}; > > > > > > #ifdef CONFIG_ZONE_DMA > > > + if (IS_ENABLED(CONFIG_ACPI)) { > > > + extern unsigned int acpi_iort_get_zone_dma_size(void); > > > > Yes as Catalin asked please add a declaration in IORT headers. > > > > Ack. > > > > + zone_dma_bits = min(zone_dma_bits, > > > + acpi_iort_get_zone_dma_size()); > > > + arm64_dma_phys_limit = max_zone_phys(zone_dma_bits); > > > + } > > > + > > > max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit); > > > #endif > > > #ifdef CONFIG_ZONE_DMA32 > > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c > > > index ec782e4a0fe4..c3db44896e49 100644 > > > --- a/drivers/acpi/arm64/iort.c > > > +++ b/drivers/acpi/arm64/iort.c > > > @@ -1722,3 +1722,54 @@ void __init acpi_iort_init(void) > > > > > > iort_init_platform_devices(); > > > } > > > + > > > +#ifdef CONFIG_ZONE_DMA > > > +/* > > > + * Check the IORT whether any devices exist whose DMA mask is < 32 bits. > > > + * If so, return the smallest value encountered, or 32 otherwise. > > > + */ > > > +unsigned int __init acpi_iort_get_zone_dma_size(void) > > > +{ > > > + struct acpi_table_iort *iort; > > > + struct acpi_iort_node *node, *end; > > > + acpi_status status; > > > + u8 limit = 32; > > > + int i; > > > + > > > + if (acpi_disabled) > > > + return limit; > > > + > > > + status = acpi_get_table(ACPI_SIG_IORT, 0, > > > + (struct acpi_table_header **)&iort); > > > + if (ACPI_FAILURE(status)) > > > + return limit; > > > + > > > + node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset); > > > + end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length); > > > + > > > + for (i = 0; i < iort->node_count; i++) { > > > + if (node >= end) > > > + break; > > > + > > > + switch (node->type) { > > > + struct acpi_iort_named_component *ncomp; > > > + struct acpi_iort_root_complex *rc; > > > + > > > + case ACPI_IORT_NODE_NAMED_COMPONENT: > > > + ncomp = (struct acpi_iort_named_component *)node->node_data; > > > + if (ncomp->memory_address_limit) > > > + limit = min(limit, ncomp->memory_address_limit); > > > + break; > > > + > > > + case ACPI_IORT_NODE_PCI_ROOT_COMPLEX: > > > + rc = (struct acpi_iort_root_complex *)node->node_data; > > > + if (rc->memory_address_limit); > > > > You need a node->revision check here otherwise we may end up > > dereferencing junk. AKA ACPI versioning in all its glory. > > > > The address limit field was there since the beginning, and DEN0049B > defines its value as 0x0, so I don't think we need to check anything > here. > > > > Thanks, > > Lorenzo > > > > > + limit = min(limit, rc->memory_address_limit); > > > + break; > > > + } > > > + node = ACPI_ADD_PTR(struct acpi_iort_node, node, node->length); > > > + } > > > + acpi_put_table(&iort->header); > > > + return limit; > > > +} > > > +#endif > > > -- > > > 2.17.1 > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel