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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 952CAC433E7 for ; Tue, 13 Oct 2020 11:24:10 +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 07689214D8 for ; Tue, 13 Oct 2020 11:24:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="IUr/snnB"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="r5hapjkC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07689214D8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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:To:Subject:Message-ID:Date:From:In-Reply-To: References:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=bb+mqv9ZvmhVDMrV1GZR3P21b+9DGaGJVgqRDYziAao=; b=IUr/snnBvCdk1h8NxJwr+4YK0 hpFUD9D1eTy1rB2GPy9KCgypJ9zz+XSZtIado/zMrObp0vXLPF8gqmjfzA22EfWMaoqCnjLbB2ssY +nIWXVzwHVxRHxv9u+Xrjv84OEhVysGF3wJuocVQZjAL/eykasnFhEIxhAEyizbuLF9JLDO4y7cFn UkxwTx4xOXphG1qVurDkR/Imfo4Lp1LA4XW9Lq2/HihXKM+rvTLq/El5IAnblotkj2sghdx+UXMVe xdM9S3p1VdrtgNIljE8HP4cBWq91phy8bdsET6CAQxl8dUZ1xifwFXQkqHcspKNHA0GvGvqHc2vzV DYYrN6y1g==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSIOH-0002ZD-1H; Tue, 13 Oct 2020 11:22:49 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSIOD-0002Ym-Pz for linux-arm-kernel@lists.infradead.org; Tue, 13 Oct 2020 11:22:46 +0000 Received: from mail-oi1-f178.google.com (mail-oi1-f178.google.com [209.85.167.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9B8E3214DB for ; Tue, 13 Oct 2020 11:22:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602588164; bh=WDLEy9dTp8uiuY+FHHNlP2miQGtmA6KUdWtVclQfV2U=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=r5hapjkCRPomwPHkFWfdvxJh1SD25oaVScv5AULcSp853skzz1c799oiyiqLeigkx 5ZjqrgNrDkgKuFwLJNqG0BHFz01qVVVhNT0eJ+X9nxSWd1bMC/IzWCQA/YHnRNeBD2 AQ5jpN+LUPm/FrG92mREyRIEnRMg0f3zsMCT/GOE= Received: by mail-oi1-f178.google.com with SMTP id u17so22110836oie.3 for ; Tue, 13 Oct 2020 04:22:44 -0700 (PDT) X-Gm-Message-State: AOAM532iwEoGNLp7BdsHn3uZtY3T9Gsh08WF8+iH/QtvTPiDo9ij6xQ+ 0DGnezksLdVYBys2gGdjgEOffs1HI6kGwzAjMX0= X-Google-Smtp-Source: ABdhPJxaz43DTCgttXXo6yRUKUHsKuUdI8PiWomqzpFi2WzgelX2W4GwrHqnAVhzNMlGEX7eQf/1nyRsx5sq2o2T6wY= X-Received: by 2002:aca:4085:: with SMTP id n127mr5604236oia.33.1602588163847; Tue, 13 Oct 2020 04:22:43 -0700 (PDT) MIME-Version: 1.0 References: <20201010093153.30177-1-ardb@kernel.org> <20201013110929.GB20319@e121166-lin.cambridge.arm.com> In-Reply-To: <20201013110929.GB20319@e121166-lin.cambridge.arm.com> From: Ard Biesheuvel Date: Tue, 13 Oct 2020 13:22:32 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] arm64: mm: set ZONE_DMA size based on early IORT scan To: Lorenzo Pieralisi X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201013_072245_999926_C6E9655C X-CRM114-Status: GOOD ( 50.66 ) 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, 13 Oct 2020 at 13:09, Lorenzo Pieralisi wrote: > > 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. > 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. > > 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