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Tsirkin" To: Cornelia Huck Subject: Re: [RFC 0/4] Enable virtio-fs on s390x Message-ID: <20200702060008-mutt-send-email-mst@kernel.org> References: <20200625100430.22407-1-mhartmay@linux.ibm.com> <20200629125305.GH31392@stefanha-x1.localdomain> <20200629130716.GQ1298906@redhat.com> <20200630090451.GE81930@stefanha-x1.localdomain> <20200630113932.484b3fde.cohuck@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200630113932.484b3fde.cohuck@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/02 03:23:40 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: 2 X-Spam_score: 0.2 X-Spam_bar: / X-Spam_report: (0.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Stefan Hajnoczi , qemu-devel@nongnu.org, Halil Pasic , Marc Hartmayer , Stefan Hajnoczi , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jun 30, 2020 at 11:39:32AM +0200, Cornelia Huck wrote: > On Tue, 30 Jun 2020 10:04:51 +0100 > Stefan Hajnoczi wrote: > > > On Mon, Jun 29, 2020 at 02:07:16PM +0100, Daniel P. Berrangé wrote: > > > On Mon, Jun 29, 2020 at 01:53:05PM +0100, Stefan Hajnoczi wrote: > > > > On Thu, Jun 25, 2020 at 12:04:26PM +0200, Marc Hartmayer wrote: > > > > > This RFC is about enabling virtio-fs on s390x. For that we need > > > > > + some shim code (first patch), and we need > > > > > + libvhost-user to deal with virtio endiannes as mandated by the spec. > > > > > > > > > > The second part is trickier, because unlike QEMU we are not certain > > > > > about the guest's native endianness, which is needed to handle the > > > > > legacy-interface appropriately. In fact, this is the reason why just > > > > > RFC. > > > > > > > > > > One of the open questions is whether to build separate versions, one > > > > > for guest little endian and one for guest big endian, or do we want > > > > > something like a command line option? (Digression on the libvirt > > > > > modeling) > > > > > > > > > > A third option would be to refuse legacy altogether. > > > > > > > > I suggest the following: > > > > > > > > 1. Combinations that worked with libvhost-user in the past must not break. > > > > > > > > 2. New combinations should only support VIRTIO 1.0 and later. > > > > > > > > This means continue to allow Legacy mode devices where they already run > > > > today but don't add new code for the cases that didn't work. > > > > > > What I'm missing here is what PCI product ID was being used when the > > > current impl is in legacy/transitional mode ? > > > > > > Normally legacy and transitional mode devices need an explicit PCI ID > > > reserved, where as modern-only devices have a PCI ID derived from their > > > VirtIO ID + a fixed offset. > > > > > > Was this mistakenly using a VirtIO ID + fixed offset for the legacy > > > mode too ? > > > > vhost-user-fs-pci does not support Legacy or Transitional mode. See > > hw/virtio/vhost-user-fs-pci.c: > > > > static const VirtioPCIDeviceTypeInfo vhost_user_fs_pci_info = { > > .base_name = TYPE_VHOST_USER_FS_PCI, > > .non_transitional_name = "vhost-user-fs-pci", > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > .instance_size = sizeof(VHostUserFSPCI), > > .instance_init = vhost_user_fs_pci_instance_init, > > .class_init = vhost_user_fs_pci_class_init, > > }; > > This makes it very unlikely that someone accidentally configures > non-modern, but does not prevent it AFAICS. See > <20200630113527.7b27f34f.cohuck@redhat.com>, which I just sent. > > (I may be off, because that is all very confusing...) Right. We'll block legacy for modern only devices going forward. Going back to the patchset in question, virtio-fs is modern only, legacy will not be supported. -- MST