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[209.51.188.17]) by mx.google.com with ESMTPS id q126si18293728iod.60.2021.03.04.00.15.56 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Thu, 04 Mar 2021 00:15:57 -0800 (PST) Received-SPF: pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; dkim=fail header.i=@redhat.com header.s=mimecast20190719 header.b="c/+HE3Y7"; spf=pass (google.com: domain of qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([::1]:44694 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lHj9I-0008KZ-Fd for alex.bennee@linaro.org; Thu, 04 Mar 2021 03:15:56 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:51754) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lHj93-0008Jz-TC for qemu-arm@nongnu.org; Thu, 04 Mar 2021 03:15:41 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:20080) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lHj92-0004Of-3F for qemu-arm@nongnu.org; Thu, 04 Mar 2021 03:15:41 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614845739; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=34rjzd6AAxkrpEEYZ4DLsWOXcHdJKGeBfYvBYFuNgT4=; b=c/+HE3Y7V09a+zvfVRKKgp5P7ELVeFRkLoqPK5umi5Y8i8+uhrw8hWB+hpzfV3qPuK9wXY nkdyWoXFx8/Sm51+pkErs5vSuDHT4uvdGTJuxZ8jU51aQOom+syFNELppVo5QHhBvVY2PQ eosClgdXN3ti6LiFhr5hXsqRTHZ44rk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-11-SiqyF2EuNJ6UOZfXgFeb_A-1; Thu, 04 Mar 2021 03:15:36 -0500 X-MC-Unique: SiqyF2EuNJ6UOZfXgFeb_A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EAA1E80432E; Thu, 4 Mar 2021 08:15:34 +0000 (UTC) Received: from [10.36.113.171] (ovpn-113-171.ams2.redhat.com [10.36.113.171]) by smtp.corp.redhat.com (Postfix) with ESMTP id 812C9614F5; Thu, 4 Mar 2021 08:15:29 +0000 (UTC) Subject: Re: [PATCH v1] acpi: increase maximum size for "etc/table-loader" blob To: Laszlo Ersek , Igor Mammedov References: <20210301104833.45580-1-david@redhat.com> <20210302172323.6cac394a@MiWiFi-RA69-srv> <09fbdaa9-2882-2056-a5a2-2ca0da8c12cf@redhat.com> <7d8281a8-0479-ac81-c602-ed87c71ce3e2@redhat.com> <4bc8c306-48d2-8122-c096-dcac15170791@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <29a6df4e-46a8-98df-99a0-68bb09cfa3bb@redhat.com> Date: Thu, 4 Mar 2021 09:15:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <4bc8c306-48d2-8122-c096-dcac15170791@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , "Michael S. Tsirkin" , Richard Henderson , qemu-devel@nongnu.org, Alistair Francis , Shannon Zhao , qemu-arm@nongnu.org, Paolo Bonzini Errors-To: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-arm" X-TUID: p4lxFpJ/q8yP On 03.03.21 16:03, Laszlo Ersek wrote: > On 03/02/21 19:43, David Hildenbrand wrote: > >> We are dealing with different blobs here (tables_blob vs. cmd_blob). > > OK, thanks -- this was the important bit I was missing. Over time I've > lost track of the actual set of fw_cfg blobs that QEMU exposes, for the > purposes of the ACPI linker/loader. > > I've looked up the acpi_add_rom_blob() calls in "hw/i386/acpi-build.c" > and "hw/arm/virt-acpi-build.c": > > hw name max_size notes > ------- ------------------------------------------- ------------------------------------ ------ > > virt ACPI_BUILD_TABLE_FILE ("etc/acpi/tables") ACPI_BUILD_TABLE_MAX_SIZE (0x200000) n/a > virt ACPI_BUILD_LOADER_FILE ("etc/table-loader") 0 n/a > virt ACPI_BUILD_RSDP_FILE ("etc/acpi/rsdp") 0 simply modeled on i386 (below) > > i386 ACPI_BUILD_TABLE_FILE ("etc/acpi/tables") ACPI_BUILD_TABLE_MAX_SIZE (0x200000) n/a > i386 ACPI_BUILD_LOADER_FILE ("etc/table-loader") 0 n/a > i386 ACPI_BUILD_RSDP_FILE ("etc/acpi/rsdp") 0 d70414a5788c, 358774d780ee8 > > microvm ACPI_BUILD_TABLE_FILE ("etc/acpi/tables") ACPI_BUILD_TABLE_MAX_SIZE (0x200000) n/a > microvm "etc/table-loader" 0 no macro for name??? > microvm ACPI_BUILD_RSDP_FILE ("etc/acpi/rsdp") 0 simply modeled on i386 (above) > > (I notice there are some other (optional) fw_cfg blobs too, related TPM, > vmgenid, nvdimm etc, using fw_cfg_add_file() rather than > acpi_add_rom_blob() -- so those are immutable (never regenerated). I > definitely needed this reminder...) > > So, my observations: > > (1) microvm open-codes "etc/table-loader", rather than using the macro > ACPI_BUILD_LOADER_FILE. > > The proposed patch corrects it, which I welcome per se. However, it > should arguably be a separate patch. I found it distracting, in spite of > the commit message highlighting it. I don't insist though, I'm > admittedly rusty on this code. > > > (2) The proposed patch sets "max_size" to ACPI_BUILD_LOADER_MAX_SIZE for > each ACPI_BUILD_LOADER_FILE. Makes sense, upon constructing / reviewing > the above table. > > (I'm no longer sure if tweaking the alignment were the preferable path > forward.) > > Either way, I'd request including the above table in the commit message. > (Maybe drop the "notes" column.) > > > (3) The above 9 invocations are *all* of the acpi_add_rom_blob() > invocations. I find the interface brittle. It's not helpful to have so > many macros for the names and the max sizes. We should have a table with > three entries and -- minimally -- two columns, specifying name and > max_size -- possibly some more call arguments, if such can be extracted. > We should also have an enum type for selecting a row in this table, and > then acpi_add_rom_blob() should be called with an enum constant. > > Of course, talk is cheap. :) > > > (4) When do we plan to introduce a nonzero "max_size" for > ACPI_BUILD_RSDP_FILE ("etc/acpi/rsdp")? > > Is the current zero value a time bomb? > > Put differently: acpi_add_rom_blob() should be *impossible* to call with > "max_size=0", arguably. *Whenever* we call acpi_add_rom_blob(), we do > that because the blob is resizable (mutable) -- but that also means we > should have a safety margin, does it not? So calling acpi_add_rom_blob() > with "max_size=0" looks self-contradictory. > > FWIW, this could be covered by the table proposed in point (3). > > > In total, I don't disagree with the patch (beyond the fact that the new > macro's value doesn't match the commit message), functionally speaking. > However, wrt. readability, I think the patch further complicates the > code. I'd suggest five patches: > > #1 -- use "etc/table-loader" via the proper macro name in "microvm", > > #2 -- rework acpi_add_rom_blob() for using a table of constants + an > enum type, > > #3 -- bump the "max_size" field for ACPI_BUILD_LOADER_FILE, for the > current symptom, > > #4 -- set a nonzero "max_size" for the remaining ACPI_BUILD_RSDP_FILE, > for "future-proofing", > > #5 -- in the new acpi_add_rom_blob() implementation, taking the enum, > assert(max_size != 0). > Mostly sounds sane to me, however, I'm leaning towards putting the real fix upfront (so we e.g., can easily backport to stable) and doing all the refactorings on top. I think we have an agreement that the current approach is the right one. I'll look into it today. Thanks! -- Thanks, David / dhildenb