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 CECD9C001DE for ; Fri, 28 Jul 2023 14:57:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qPObC-0007BN-IE; Fri, 28 Jul 2023 10:37:46 -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 1qPObB-0007BE-Px for qemu-devel@nongnu.org; Fri, 28 Jul 2023 10:37:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qPObA-0004EO-6s for qemu-devel@nongnu.org; Fri, 28 Jul 2023 10:37:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1690555063; h=from:from:reply-to: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=d9FOSInf8Ut/953lgSDq5wY4XvPS8dEecrDSEKLwY2U=; b=ZzOciRql4oqk5hUQusBGX82XAhYWLqXNuGke1kQ6Ah7Z47MN6a0xu2q6KXpaD+vwn35Kqc UNv42v7YMaQHGxF9c+dZApPGDERr/dHHYuxiWGGXS3zkvSNQf1SQAQzi0nx2jjN5g54k6a QSapKkxCXygWiy83CDC/W8+U2RrhS9Y= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-632-wRMSQ_jTOd-2lszji7rEMQ-1; Fri, 28 Jul 2023 10:37:39 -0400 X-MC-Unique: wRMSQ_jTOd-2lszji7rEMQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0FD5C1C0725A; Fri, 28 Jul 2023 14:37:39 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2A24A1121330; Fri, 28 Jul 2023 14:37:38 +0000 (UTC) Date: Fri, 28 Jul 2023 15:37:36 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Thomas Huth Cc: qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Stefan Weil , Yonggang Luo , Peter Maydell Subject: Re: [RFC PATCH 4/6] hw/i386/intel_iommu: Fix VTD_IR_TableEntry for ms_struct layout Message-ID: References: <20230728142748.305341-1-thuth@redhat.com> <20230728142748.305341-5-thuth@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230728142748.305341-5-thuth@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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, T_SCC_BODY_TEXT_LINE=-0.01 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Jul 28, 2023 at 04:27:46PM +0200, Thomas Huth wrote: > We might want to compile QEMU with Clang on Windows - but it > does not support the __attribute__((gcc_struct)) yet. So we > have to make sure that the structs will stay the same when > the compiler uses the "ms_struct" layout. The VTD_IR_TableEntry > struct is affected - rewrite it a little bit so that it works > fine with both struct layouts. > > Reported-by: Daniel P. Berrangé > Signed-off-by: Thomas Huth > --- > include/hw/i386/intel_iommu.h | 14 ++++++++------ > hw/i386/intel_iommu.c | 2 +- > 2 files changed, 9 insertions(+), 7 deletions(-) > > diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h > index 89dcbc5e1e..08bf220393 100644 > --- a/include/hw/i386/intel_iommu.h > +++ b/include/hw/i386/intel_iommu.h > @@ -204,18 +204,20 @@ union VTD_IR_TableEntry { > #endif > uint32_t dest_id; /* Destination ID */ > uint16_t source_id; /* Source-ID */ > + uint16_t __reserved_2; /* Reserved 2 */ > #if HOST_BIG_ENDIAN > - uint64_t __reserved_2:44; /* Reserved 2 */ > - uint64_t sid_vtype:2; /* Source-ID Validation Type */ > - uint64_t sid_q:2; /* Source-ID Qualifier */ > + uint32_t __reserved_3:28; /* Reserved 3 */ > + uint32_t sid_vtype:2; /* Source-ID Validation Type */ > + uint32_t sid_q:2; /* Source-ID Qualifier */ > #else > - uint64_t sid_q:2; /* Source-ID Qualifier */ > - uint64_t sid_vtype:2; /* Source-ID Validation Type */ > - uint64_t __reserved_2:44; /* Reserved 2 */ > + uint32_t sid_q:2; /* Source-ID Qualifier */ > + uint32_t sid_vtype:2; /* Source-ID Validation Type */ > + uint32_t __reserved_3:28; /* Reserved 3 */ Hasn't this has changed the struct layout in the else clause Old layout: source_id : 16 sid_q : 2 sid_vtype : 2 reserved_2 : 44 New layout source_id : 16 reserved_2 : 16 sid_q : 2 sid_vtype : 2 reserved_3 : 28 Was there something wrong with the change I suggested to just make source_id be a bitfield too: uint64_t source_id: 16; /* Source-ID */ which could make ms_struct layout avoid padding to the following bitfields. > #endif > } QEMU_PACKED irte; > uint64_t data[2]; > }; With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|