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Tsirkin" Cc: Cornelia Huck , Jason Wang , Xie Yongji , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, markver@us.ibm.com, Christian Borntraeger , linux-s390@vger.kernel.org, virtio-dev@lists.oasis-open.org, Halil Pasic Subject: Re: [virtio-dev] Re: [RFC PATCH 1/1] virtio: write back features before verify Message-ID: <20211005131751.53175b10.pasic@linux.ibm.com> In-Reply-To: <20211004160005-mutt-send-email-mst@kernel.org> References: <87fstm47no.fsf@redhat.com> <20211002141351-mutt-send-email-mst@kernel.org> <20211003070030.658fc94e.pasic@linux.ibm.com> <20211003021027-mutt-send-email-mst@kernel.org> <20211003032253-mutt-send-email-mst@kernel.org> <87ee912e45.fsf@redhat.com> <20211004083455-mutt-send-email-mst@kernel.org> <878rz83lx0.fsf@redhat.com> <20211004110152-mutt-send-email-mst@kernel.org> <87zgro23r1.fsf@redhat.com> <20211004160005-mutt-send-email-mst@kernel.org> Organization: IBM X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 9gaiqSXmPn_x9AjMuITDUyXUKN9UZVPY X-Proofpoint-ORIG-GUID: NtvF1X0oiMGcW3bFKnAES-ppYgqouYHn X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-10-04_05,2021-10-04_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 spamscore=0 phishscore=0 impostorscore=0 mlxscore=0 malwarescore=0 mlxlogscore=999 adultscore=0 priorityscore=1501 clxscore=1011 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2110050065 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 4 Oct 2021 16:01:12 -0400 "Michael S. Tsirkin" wrote: > > > > Ok, so what about something like > > > > "If FEATURES_OK is not set, the driver MAY change the set of features it > > accepts." > > > > in the device initialization section? > > Maybe "as long as". However Halil implied that some features are not > turned off properly if that happens. Halil could you pls provide > some examples? static void virtio_net_set_features(VirtIODevice *vdev, uint64_t features) { ... if (virtio_has_feature(features, VIRTIO_NET_F_STANDBY)) { qapi_event_send_failover_negotiated(n->netclient_name); qatomic_set(&n->failover_primary_hidden, false); failover_add_primary(n, &err); if (err) { warn_report_err(err); } } } This is probably the only one in QEMU. Back then I stopped looking after the first hit. Regards, Halil