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bh=wBUWhF9L5WBk5Y70g2h4OMjzxnq8q+5HHQCHjSXPHwc=; b=MCMfuKVHlw9bmv6CHBdVt8Eb/3yI2gn5pBjnnvFLGcKEsrXFj5O30klSFH+NNxcRCE6jmA 3JWDF/QDnkhS7CvuE9nVmVBQtir/ulTMk+KeZgXcmOKsEkYVThr0Hza5MghRu4GWSse6NG qTDTGN7dRjnS6B0M2PuhdauwcOV21/s= 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-123-I_3CF5EqNBWj5RyVfOCS3g-1; Tue, 17 Nov 2020 14:22:03 -0500 X-MC-Unique: I_3CF5EqNBWj5RyVfOCS3g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 662C28049C9; Tue, 17 Nov 2020 19:22:01 +0000 (UTC) Received: from thuth.remote.csb (ovpn-113-138.ams2.redhat.com [10.36.113.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id A714419D6C; Tue, 17 Nov 2020 19:21:52 +0000 (UTC) Subject: Re: [PATCH for-5.2] s390x/pci: fix endianness issues To: Cornelia Huck , Matthew Rosato References: <20201117171340.1289659-1-cohuck@redhat.com> From: Thomas Huth Message-ID: <6a1b2ba1-642a-9cee-4d7d-2c1e4ea826ed@redhat.com> Date: Tue, 17 Nov 2020 20:21:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201117171340.1289659-1-cohuck@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/17 01:18:45 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, T_SPF_TEMPERROR=0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alex Williamson , Pierre Morel , David Hildenbrand , Richard Henderson , qemu-devel@nongnu.org, Halil Pasic , Christian Borntraeger , qemu-s390x@nongnu.org, =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17/11/2020 18.13, Cornelia Huck wrote: > zPCI control blocks are big endian, we need to take care that we > do proper accesses in order not to break tcg guests on little endian > hosts. > > Fixes: 28dc86a07299 ("s390x/pci: use a PCI Group structure") > Fixes: 9670ee752727 ("s390x/pci: use a PCI Function structure") > Fixes: 1e7552ff5c34 ("s390x/pci: get zPCI function info from host") This fixes the problem with my old Fedora 28 under TCG, too, but... do we really want to store this information in big endian on the QEMU side (e.g. in the QTAILQ lists)? ... that smells like trouble again in the future... I think it would be better if we rather replace all those memcpy() functions in the patches that you cited in the "Fixes:" lines above with code that changes the endianess when we copy the date from QEMU space to guest space and vice versa. What do you think? Thomas