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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EB453CA100D for ; Tue, 5 Sep 2023 20:45:03 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qdcu8-0001HA-Fa; Tue, 05 Sep 2023 16:44:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qdcu7-0001Gg-5O for qemu-devel@nongnu.org; Tue, 05 Sep 2023 16:44:07 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qdcu3-0000mD-2v for qemu-devel@nongnu.org; Tue, 05 Sep 2023 16:44:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693946641; 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: in-reply-to:in-reply-to:references:references; bh=jJnWyERjpXcZTAMTv8MbDjaow04MVwSMqfbZSI0pog4=; b=BESrU++Hbqx/l/VrCVAvgZ5uEFYSKWibjIIX415IhgexTC5cCyGzdLmPNJVYDw6k66ogDv BF/yzqes/CYDrBANAxOOENWtRocf1h6unSvOSqKPvcsvMLkR0OGxfLFz1fEZRvUiCx8UVy /gRoMlzfX1T546ZMVA92vckcnbyvB2c= Received: from mail-lf1-f72.google.com (mail-lf1-f72.google.com [209.85.167.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-453-KJm1HXaHNUOXk8nWe9zvyw-1; Tue, 05 Sep 2023 16:44:00 -0400 X-MC-Unique: KJm1HXaHNUOXk8nWe9zvyw-1 Received: by mail-lf1-f72.google.com with SMTP id 2adb3069b0e04-500b5641eeaso3149544e87.3 for ; Tue, 05 Sep 2023 13:44:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693946639; x=1694551439; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=jJnWyERjpXcZTAMTv8MbDjaow04MVwSMqfbZSI0pog4=; b=k6HKLqyXmmn/g2+Hld7MenYCohAMIJvSVW1EQTDjJU7RBKyohec94k4uNOf5FxBJvT grnBd0IC2ZebHS4FRynJbt7EyN82h5aOMO8bkPV0rfX0flBMkkrgVU1f6nLW63fPNxqQ qOVr8O63+SmwotuqXgolRUW5WXWiUoftJ2XQRQUhhNAiMd7psxvQZYS0EU5X5AePY2bF tt5bArTEw2IK1VWX21RdiMgx8GaYMH6nGiK++YT28xPvpsP6oNKxKHpzsqKkRE5oY8Uj BHOgrDixvlygopXrP40Xmmg7W4tNqFZO5LoS7PClEHk3Xe7oyfOmzNoAgIOocdLmcic1 fF0w== X-Gm-Message-State: AOJu0YxYvQm2SZ7yIzeLRIEEsxjYoLnnFSoBMnnNqU+8LlBfhN9esWu9 VhWyIN7+SKn3J+HEPQwhfyjBzPWBMwX2nZ4EP0TCikkXd+LbnA6+6puor5h/aswbotuIXsvudjj 0zUKh4u4ah3v9vyc= X-Received: by 2002:a19:2d4c:0:b0:500:b7ed:105a with SMTP id t12-20020a192d4c000000b00500b7ed105amr582903lft.29.1693946639065; Tue, 05 Sep 2023 13:43:59 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFnL41Xxx1YeqPUIEA4QvibMnyDvFNiyTmB6SxKksTkLbDW9Fcdqxd11huwMJWqJwuoXV/BGA== X-Received: by 2002:a19:2d4c:0:b0:500:b7ed:105a with SMTP id t12-20020a192d4c000000b00500b7ed105amr582888lft.29.1693946638696; Tue, 05 Sep 2023 13:43:58 -0700 (PDT) Received: from redhat.com ([2.52.23.134]) by smtp.gmail.com with ESMTPSA id b4-20020aa7c6c4000000b00523653295f9sm7455175eds.94.2023.09.05.13.43.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Sep 2023 13:43:57 -0700 (PDT) Date: Tue, 5 Sep 2023 16:43:54 -0400 From: "Michael S. Tsirkin" To: Marcello Sylverster Bauer Cc: qemu-devel@nongnu.org, imammedo@redhat.com, ani@anisinha.ca, Patrick Rudolph Subject: Re: PCI Hotplug ACPI device names only 3 characters long Message-ID: <20230905163919-mutt-send-email-mst@kernel.org> References: <66949448-1577-444a-b6d2-d907f9870765@sylv.io> <20230905123447-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=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-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Sep 05, 2023 at 07:45:12PM +0200, Marcello Sylverster Bauer wrote: > Hi Michael, > > On 9/5/23 18:44, Michael S. Tsirkin wrote: > > On Tue, Sep 05, 2023 at 05:05:33PM +0200, Marcello Sylverster Bauer wrote: > > > Greetings, > > > > > > I'm currently working on a project to support Intel IPU6 in QEMU via VFIO so > > > that the guest system can access the camera. This requires extending the > > > ACPI device definition so that the guest knows how to access the camera. > > > > > > However, I cannot extend the PCI devices because their names are not 4 > > > characters long and therefore do not follow the ACPI specification. > > > > > > When I use '-acpitable' to include my own SSDT for the IPU6 PCI device, it > > > does not allow me to declare the device as an External Object because it > > > automatically adds padding underscores. > > > > > > e.g. > > > Before: > > > ``` > > > External(_SB.PCI0.S18.SA0, DeviceObj) > > > ``` > > > After: > > > ``` > > > External(_SB.PCI0.S18_.SA0_, DeviceObj) > > > ``` > > > > > > Adding the underscore padding is hard coded in iASL and also in QEMU when > > > parsing an ASL file. (see: build_append_nameseg()) > > > > > > So here are my questions: > > > 1. Is there a solution to extend the ACPI PCI device using '-acpitable' > > > without having to patch iASL or QEMU? > > > 2. Are there any plans to change the names to comply with the ACPI spec? > > > (e.g. use "S%.03X" format string instead) > > > > > > Thanks > > > Marcello > > > > > > 1. All names in ACPI are always exactly 4 characters long. _ is a legal character > > but names beginning with _ are reserved. > > Exactly, which is why I want to address this issue here. Currently, Qemu > generates ACPI device names with only 3 characters. (See > build_append_pci_bus_devices() in hw/i386/acpi-build.c). > For example, the device I want to append entries to has the path > "_SB.PCI0.S18.SA0", but I can't because of the two auto-generated devices > with only 3 characters in their names. They are 4 characters otherwise OSPMs wouldn't work. In your example the path is _SB.PCI0.S18_.SA0_ - you disassembler probably just helpfully hides it for readability. > > There's no rule in ACPI > > spec that says they need to follow S%.03X or any other specific format. > > I'm pretty sure we do follow the ACPI specification in this but feel free to > > prove me wrong. > > You have misunderstood me. Currently, Qemu uses the following format to > create PCI ACPI devices: > > ``` > aml_name("S%.02X", devfn) > ``` > > My question is whether we should change it to something that results in a 4 > character name like "S%.03X" or "S%.02X_". I think you misunderstand the code. Look at build_append_nameseg and you will see that the name is always ACPI_NAMESEG_LEN characters which equals 4. > I have tested it and it works fine as long as any hardcoded path references > are adjusted. But I'm not 100% sure if this could cause any regressions. > > > 2. You can probably add something to existing ACPI devices using Scope(). > > I'm pretty sure the external object is required when loading a separate > SSDT, but I'll try by just using scopes. > > > I would not advise relying on this - current names are not a stable > > interface that we guarantee across QEMU versions. > > If adding this functionality is desirable, I think we'll need some new interface > > to set a stable ACPI name. Maybe using aliases. > > Currently I'm just working on a PoW to get IPU6 working in QEMU, so > instability is fine. > > Thanks, > Marcello > > > > >