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 742A8C47DD9 for ; Wed, 28 Feb 2024 12:38:05 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rfJBR-0005f4-Cl; Wed, 28 Feb 2024 07:37:13 -0500 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 1rfJBP-0005cz-7Q for qemu-devel@nongnu.org; Wed, 28 Feb 2024 07:37:11 -0500 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 1rfJBN-0001kz-LY for qemu-devel@nongnu.org; Wed, 28 Feb 2024 07:37:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709123828; 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=TRbHu0IyoINOPUwo8bCb35ebFaUMAVVlXB12u/DtRS4=; b=LjYDaRSoJCY5rF8lB3mI4RYT98Bmyi/4i/SR8Rjc7yZr51p5ZCnF+WX/osjUUPM0tmoM6r /FGeaAGsDMWOFst6mE/x8mm+TmJJYCNcxErev9gHC86x3eufNSBZszxF9UE8P9S268yEp/ Vl3lq6ZAY8D0X1MpMmz9zDBu5UaK/Ss= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-57-u6Y3QPPSPxayE00N4PbhTg-1; Wed, 28 Feb 2024 07:37:04 -0500 X-MC-Unique: u6Y3QPPSPxayE00N4PbhTg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9530285A59D; Wed, 28 Feb 2024 12:37:03 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 384B9492BE8; Wed, 28 Feb 2024 12:37:03 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 1C88321E66F4; Wed, 28 Feb 2024 13:36:57 +0100 (CET) From: Markus Armbruster To: Akihiko Odaki Cc: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , "Michael S. Tsirkin" , Marcel Apfelbaum , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Paolo Bonzini , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Eduardo Habkost , Sriram Yagnaraman , Jason Wang , Keith Busch , Klaus Jensen , qemu-devel@nongnu.org, qemu-block@nongnu.org Subject: Re: [PATCH v8 13/15] hw/pci: Use UINT32_MAX as a default value for rombar In-Reply-To: <20240228-reuse-v8-13-282660281e60@daynix.com> (Akihiko Odaki's message of "Wed, 28 Feb 2024 20:33:24 +0900") References: <20240228-reuse-v8-0-282660281e60@daynix.com> <20240228-reuse-v8-13-282660281e60@daynix.com> Date: Wed, 28 Feb 2024 13:36:57 +0100 Message-ID: <87zfvkvk7q.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.102, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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 Akihiko Odaki writes: > Currently there is no way to distinguish the case that rombar is > explicitly specified as 1 and the case that rombar is not specified. > > Set rombar UINT32_MAX by default to distinguish these cases just as it > is done for addr and romsize. It was confirmed that changing the default > value to UINT32_MAX will not change the behavior by looking at > occurences of rom_bar. > > $ git grep -w rom_bar > hw/display/qxl.c:328: QXLRom *rom = memory_region_get_ram_ptr(&d->rom_bar); > hw/display/qxl.c:431: qxl_set_dirty(&qxl->rom_bar, 0, qxl->rom_size); > hw/display/qxl.c:1048: QXLRom *rom = memory_region_get_ram_ptr(&qxl->rom_bar); > hw/display/qxl.c:2131: memory_region_init_rom(&qxl->rom_bar, OBJECT(qxl), "qxl.vrom", > hw/display/qxl.c:2154: PCI_BASE_ADDRESS_SPACE_MEMORY, &qxl->rom_bar); > hw/display/qxl.h:101: MemoryRegion rom_bar; > hw/pci/pci.c:74: DEFINE_PROP_UINT32("rombar", PCIDevice, rom_bar, 1), > hw/pci/pci.c:2329: if (!pdev->rom_bar) { > hw/vfio/pci.c:1019: if (vdev->pdev.romfile || !vdev->pdev.rom_bar) { > hw/xen/xen_pt_load_rom.c:29: if (dev->romfile || !dev->rom_bar) { > include/hw/pci/pci_device.h:150: uint32_t rom_bar; > > rom_bar refers to a different variable in qxl. It is only tested if > the value is 0 or not in the other places. > > If a user explicitly set UINT32_MAX, we still cannot distinguish that > from the implicit default. However, it is unlikely to be a problem as > nobody would type literal UINT32_MAX (0xffffffff or 4294967295) by > chance. > > Signed-off-by: Akihiko Odaki Not exactly elegant, but I believe we have similar "default value means not set by user (good enough because the default value is sufficiently odd)" logic elsewhere. Reviewed-by: Markus Armbruster