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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 F189EC433E7 for ; Tue, 13 Oct 2020 11:10:58 +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 893CD21548 for ; Tue, 13 Oct 2020 11:10:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="eQPWgyxj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 893CD21548 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=BX6N7yo94nKo8w6gTAr56wPR10TF8eetsnLtyzsbmBE=; b=eQPWgyxjD3rJAj/HufxWJv4ho CxpGZsij8ExIoGq2g6MYRgaG/1oFU0RZEE5CMyj+5Plu5ywsdZEPxEx8SO8PPfYXrl/MNEbeVoX/5 lkxGvB4S4qf32dawLiPE1ECtZavs5tUCT74P5iIyiaaefU0jcOIO2NeBN9dKhMnAmzcCqqj9K17xA UFD+FnOcndqY3s8OgWSstDSxD9vpZ7zA1FHb6P3MwmgBkS3g9Ifa3wr433pSjYfPcCbxJu9DIWxdo URyNixPNdqNdXGfeCHxaUlR7+Minz9znpCB1khZKRZm4R39s+amKuecGZI+Zestkmw+J0Zg5Fjj59 zIzAHdFhQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSIBW-00011s-FY; Tue, 13 Oct 2020 11:09:38 +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 1kSIBT-00010t-Ny for linux-arm-kernel@lists.infradead.org; Tue, 13 Oct 2020 11:09:36 +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 65E6D1FB; Tue, 13 Oct 2020 04:09:33 -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 B5FA23F719; Tue, 13 Oct 2020 04:09:31 -0700 (PDT) Date: Tue, 13 Oct 2020 12:09:29 +0100 From: Lorenzo Pieralisi To: Ard Biesheuvel Subject: Re: [PATCH] arm64: mm: set ZONE_DMA size based on early IORT scan Message-ID: <20201013110929.GB20319@e121166-lin.cambridge.arm.com> References: <20201010093153.30177-1-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201010093153.30177-1-ardb@kernel.org> 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_070935_866822_7AC9A453 X-CRM114-Status: GOOD ( 39.42 ) 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@arm.com, Sudeep Holla , Robin Murphy , Jeremy Linton , linux-acpi@vger.kernel.org, Rob Herring , linux-arm-kernel@lists.infradead.org, Hanjun Guo , will@kernel.org, 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 Sat, Oct 10, 2020 at 11:31:53AM +0200, Ard Biesheuvel wrote: > We recently introduced a 1 GB sized ZONE_DMA to cater for platforms > incorporating masters that can address less than 32 bits of DMA, in > particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has > peripherals that can only address up to 1 GB (and its PCIe host > bridge can only access the bottom 3 GB) > > Instructing the DMA layer about these limitations is straight-forward, > even though we had to fix some issues regarding memory limits set in > the IORT for named components, and regarding the handling of ACPI _DMA > methods. However, the DMA layer also needs to be able to allocate > memory that is guaranteed to meet those DMA constraints, for bounce > buffering as well as allocating the backing for consistent mappings. > > This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately, > it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes > problems with kdump, and potentially in other places where allocations > cannot cross zone boundaries. Therefore, we should avoid having two > separate DMA zones when possible. > > So let's do an early scan of the IORT, and only create the ZONE_DMA > if we encounter any devices that need it. This puts the burden on > the firmware to describe such limitations in the IORT, which may be > redundant (and less precise) if _DMA methods are also being provided. > However, it should be noted that this situation is highly unusual for > arm64 ACPI machines. Also, the DMA subsystem still gives precedence to > the _DMA method if implemented, and so we will not lose the ability to > perform streaming DMA outside the ZONE_DMA if the _DMA method permits > it. > > Cc: Jeremy Linton > Cc: Lorenzo Pieralisi > Cc: Nicolas Saenz Julienne > Cc: Rob Herring > Cc: Christoph Hellwig > Cc: Robin Murphy > Cc: Hanjun Guo > Cc: Sudeep Holla > Cc: Anshuman Khandual > Signed-off-by: Ard Biesheuvel > --- > This is related to the discussion in > > https://lore.kernel.org/linux-arm-kernel/20201001161740.29064-2-nsaenzjulienne@suse.de/ > > Documentation/arm64/arm-acpi.rst | 7 +++ > arch/arm64/mm/init.c | 8 +++ > drivers/acpi/arm64/iort.c | 51 ++++++++++++++++++++ > 3 files changed, 66 insertions(+) Thanks for putting it together so promptly. > 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. > 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. > + 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. 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