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=-12.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 E580BC433E0 for ; Thu, 4 Feb 2021 17:57:14 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 7C75864E24 for ; Thu, 4 Feb 2021 17:57:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C75864E24 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.81393.150381 (Exim 4.92) (envelope-from ) id 1l7is6-0006o6-AX; Thu, 04 Feb 2021 17:56:50 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 81393.150381; Thu, 04 Feb 2021 17:56:50 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l7is6-0006nz-7S; Thu, 04 Feb 2021 17:56:50 +0000 Received: by outflank-mailman (input) for mailman id 81393; Thu, 04 Feb 2021 17:56:49 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l7is5-0006nu-BL for xen-devel@lists.xenproject.org; Thu, 04 Feb 2021 17:56:49 +0000 Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id cec07597-dbc1-450e-8040-1f4b45438823; Thu, 04 Feb 2021 17:56:48 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 1FDCB64E16; Thu, 4 Feb 2021 17:56:47 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: cec07597-dbc1-450e-8040-1f4b45438823 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612461407; bh=PZM7++DFciYJIXwmZYWX3m9pNq4vqDJHiX8c5FbyRVw=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=hC/QRiIIhtm/wXGBYt57q9XtXIt/TFPFk6AsS5IEUkhd3ji+QTpYFMsKnEsUMjn9x b0u9J97Kj5hQZXpb9c2CXKCQ49pNr3FX3pQrQ6m+NV/WbBhDHQZCKx14M9MQnXbtji VMbEvHX7LDWfA3ot6CYck/4zA3NpQyxaLI/8xMyh8R13/5K47NrZxAfhQqL16Tq/hM VKDqJ13umW4ye4mG3lWGmbM1NFudbltXa/Nh5BRaD/VHEdv1HXssi9b/KGM+IOxiQw 3qxoDYV3P0tLklr5wBwP9e7OVTMAe45mhRfutPsOKJorfmKGT7cwH2zgMfveLAYHuJ 83Cw2HxwAU3gg== Date: Thu, 4 Feb 2021 09:56:46 -0800 (PST) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-T480s To: robh@kernel.org cc: Stefano Stabellini , Julien Grall , Elliott Mitchell , xen-devel , Volodymyr Babchuk , julien@xen.org Subject: Question on PCIe Device Tree bindings, Was: [PATCH] xen/arm: domain_build: Ignore device nodes with invalid addresses In-Reply-To: <9b97789b-5560-0186-642a-0501789830e5@xen.org> Message-ID: References: <06d6b9ec-0db9-d6da-e30b-df9f9381157d@xen.org> <9b97789b-5560-0186-642a-0501789830e5@xen.org> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Hi Rob, We have a question on the PCIe device tree bindings. In summary, we have come across the Raspberry Pi 4 PCIe description below: pcie0: pcie@7d500000 { compatible = "brcm,bcm2711-pcie"; reg = <0x0 0x7d500000 0x0 0x9310>; device_type = "pci"; #address-cells = <3>; #interrupt-cells = <1>; #size-cells = <2>; interrupts = , ; interrupt-names = "pcie", "msi"; interrupt-map-mask = <0x0 0x0 0x0 0x7>; interrupt-map = <0 0 0 1 &gicv2 GIC_SPI 143 IRQ_TYPE_LEVEL_HIGH>; msi-controller; msi-parent = <&pcie0>; ranges = <0x02000000 0x0 0xc0000000 0x6 0x00000000 0x0 0x40000000>; /* * The wrapper around the PCIe block has a bug * preventing it from accessing beyond the first 3GB of * memory. */ dma-ranges = <0x02000000 0x0 0x00000000 0x0 0x00000000 0x0 0xc0000000>; brcm,enable-ssc; pci@1,0 { #address-cells = <3>; #size-cells = <2>; ranges; reg = <0 0 0 0 0>; usb@1,0 { reg = <0x10000 0 0 0 0>; resets = <&reset RASPBERRYPI_FIRMWARE_RESET_ID_USB>; }; }; }; Xen fails to parse it with an error because it tries to remap reg = <0x10000 0 0 0 0> as if it was a CPU address and of course it fails. Reading the device tree description in details, I cannot tell if Xen has a bug: the ranges property under pci@1,0 means that pci@1,0 is treated like a default bus (not a PCI bus), hence, the children regs are translated using the ranges property of the parent (pcie@7d500000). Is it possible that the device tree is missing device_type = "pci" under pci@1,0? Or is it just implied because pci@1,0 is a child of pcie@7d500000? I'd like to make Xen able to parse this device tree without errors but I am not sure what is the best way to fix it. Thanks for any help you can provide! Cheers, Stefano On Thu, 4 Feb 2021, Julien Grall wrote: > On 04/02/2021 00:13, Stefano Stabellini wrote: > > On Wed, 3 Feb 2021, Julien Grall wrote: > > > On Wed, 3 Feb 2021 at 22:18, Stefano Stabellini > > > wrote: > > > > > > But aside from PCIe, let's say that we know of a few nodes for which > > > > > > "reg" needs a special treatment. I am not sure it makes sense to > > > > > > proceed > > > > > > with parsing those nodes without knowing how to deal with that. > > > > > > > > > > I believe that most of the time the "special" treatment would be to > > > > > ignore the > > > > > property "regs" as it will not be an CPU memory address. > > > > > > > > > > > So maybe > > > > > > we should add those nodes to skip_matches until we know what to do > > > > > > with > > > > > > them. At that point, I would imagine we would introduce a special > > > > > > handle_device function that knows what to do. In the case of PCIe, > > > > > > something like "handle_device_pcie". > > > > > Could you outline how "handle_device_pcie()" will differ with > > > > > handle_node()? > > > > > > > > > > In fact, the problem is not the PCIe node directly. Instead, it is the > > > > > second > > > > > level of nodes below it (i.e usb@...). > > > > > > > > > > The current implementation of dt_number_of_address() only look at the > > > > > bus type > > > > > of the parent. As the parent has no bus type and "ranges" then it > > > > > thinks this > > > > > is something we can translate to a CPU address. > > > > > > > > > > However, this is below a PCI bus so the meaning of "reg" is completely > > > > > different. In this case, we only need to ignore "reg". > > > > > > > > I see what you are saying and I agree: if we had to introduce a special > > > > case for PCI, then dt_number_of_address() seems to be a good place. In > > > > fact, we already have special PCI handling, see our > > > > __dt_translate_address function and xen/common/device_tree.c:dt_busses. > > > > > > > > Which brings the question: why is this actually failing? > > > > > > I already hinted at the reason in my previous e-mail :). Let me expand > > > a bit more. > > > > > > > > > > > pcie0 { > > > > ranges = <0x02000000 0x0 0xc0000000 0x6 0x00000000 0x0 > > > > 0x40000000>; > > > > > > > > Which means that PCI addresses 0xc0000000-0x100000000 become > > > > 0x600000000-0x700000000. > > > > > > > > The offending DT is: > > > > > > > > &pcie0 { > > > > pci@1,0 { > > > > #address-cells = <3>; > > > > #size-cells = <2>; > > > > ranges; > > > > > > > > reg = <0 0 0 0 0>; > > > > > > > > usb@1,0 { > > > > reg = <0x10000 0 0 0 0>; > > > > resets = <&reset > > > > RASPBERRYPI_FIRMWARE_RESET_ID_USB>; > > > > }; > > > > }; > > > > }; > > > > > > > > > > > > reg = <0x10000 0 0 0 0> means that usb@1,0 is PCI device 01:00.0. > > > > However, the rest of the regs cells are left as zero. It shouldn't be an > > > > issue because usb@1,0 is a child of pci@1,0 but pci@1,0 is not a bus. > > > > > > The property "ranges" is used to define a mapping or translation > > > between the address space of the "bus" (here pci@1,0) and the address > > > space of the bus node's parent (&pcie0). > > > IOW, it means "reg" in usb@1,0 is an address on the PCI bus (i.e. BDF). > > > > > > The problem is dt_number_of_address() will only look at the "bus" type > > > of the parent using dt_match_bus(). This will return the default bus > > > (see dt_bus_default_match()), because this is a property "ranges" in > > > the parent node (i.e. pci@1,0). Therefore... > > > > > > > So > > > > in theory dt_number_of_address() should already return 0 for it. > > > > > > ... dt_number_of_address() will return 1 even if the address is not a > > > CPU address. So when Xen will try to translate it, it will fail. > > > > > > > > > > > Maybe reg = <0 0 0 0 0> is the problem. In that case, we could simply > > > > add a check to skip 0 size ranges. Just a hack to explain what I mean: > > > > > > The parent of pci@1,0 is a PCI bridge (see the property type), so the > > > CPU addresses are found not via "regs" but "assigned-addresses". > > > > > > In this situation, "regs" will have a different meaning and therefore > > > there is no promise that the size will be 0. > > > > I copy/pasted the following: > > > > pci@1,0 { > > #address-cells = <3>; > > #size-cells = <2>; > > ranges; > > > > reg = <0 0 0 0 0>; > > > > usb@1,0 { > > reg = <0x10000 0 0 0 0>; > > resets = <&reset > > RASPBERRYPI_FIRMWARE_RESET_ID_USB>; > > }; > > }; > > > > under pcie0 in my DTS to see what happens (the node is not there in the > > device tree for the rpi-5.9.y kernel.) It results in the expected error: > > > > (XEN) Unable to retrieve address 0 for /scb/pcie@7d500000/pci@1,0/usb@1,0 > > (XEN) Device tree generation failed (-22). > > > > I could verify that pci@1,0 is seen as "default" bus due to the range > > property, thus dt_number_of_address() returns 1. > > > > > > I can see that reg = <0 0 0 0 0> is not a problem because it is ignored > > given that the parent is a PCI bus. assigned-addresses is the one that > > is read. > > > > > > But from a device tree perspective I am actually confused by the > > presence of the "ranges" property under pci@1,0. Is that correct? It is > > stating that addresses of children devices will be translated to the > > address space of the parent (pcie0) using the parent translation rules. > > I mean -- it looks like Xen is right in trying to translate reg = > > <0x10000 0 0 0 0> using ranges = <0x02000000 0x0 0xc0000000 0x6 > > 0x00000000 0x0 0x40000000>. > > > > Or maybe since pcie0 is a PCI bus all the children addresses, even > > grand-children, are expected to be specified using "assigned-addresses"? > > > > > > Looking at other examples [1][2] maybe the mistake is that pci@1,0 is > > missing device_type = "pci"? Of course, if I add that, the error > > disappear. > > I am afraid, I don't know the answer. I think it would be best to ask the > Linux DT folks about it. > > > > > [1] Documentation/devicetree/bindings/pci/mvebu-pci.txt > > [2] Documentation/devicetree/bindings/pci/nvidia,tegra20-pcie.txt > > > > For the sake of making Xen more resilient to possible DTSes, maybe we > > should try to extend the dt_bus_pci_match check? See for instance the > > change below, but we might be able to come up with better ideas. > > > > > > diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c > > index 18825e333e..24d998f725 100644 > > --- a/xen/common/device_tree.c > > +++ b/xen/common/device_tree.c > > @@ -565,12 +565,21 @@ static unsigned int dt_bus_default_get_flags(const > > __be32 *addr) > > static bool_t dt_bus_pci_match(const struct dt_device_node *np) > > { > > + bool ret = false; > > + > > /* > > * "pciex" is PCI Express "vci" is for the /chaos bridge on 1st-gen > > PCI > > * powermacs "ht" is hypertransport > > */ > > - return !strcmp(np->type, "pci") || !strcmp(np->type, "pciex") || > > + ret = !strcmp(np->type, "pci") || !strcmp(np->type, "pciex") || > > !strcmp(np->type, "vci") || !strcmp(np->type, "ht"); > > + > > + if ( ret ) return ret; > > + > > + if ( !strcmp(np->name, "pci") ) > > + ret = dt_bus_pci_match(dt_get_parent(np)); > > It is probably safe to assume that a PCI device (not hostbridge) will start > with "pci". Although, I don't much like the idea because the name is not meant > to be stable. > > AFAICT, we can only rely on "compatible" and "type". > > Cheers, > > -- > Julien Grall >