virtio — archive

[Michael S. Tsirkin <david.edmondson@oracle.com>]

On Wed, Mar 08, 2023 at 03:02:05PM +0100, Jiri Pirko wrote: > Wed, Mar 08, 2023 at 02:44:08PM CET, david.edmondson@oracle.com wrote: > >Jiri Pirko <jiri@nvidia.com> writes: > > > >> Wed, Mar 08, 2023 at 01:59:10PM CET, david.edmondson@oracle.com wrote: > >>>"Michael S. Tsirkin" <mst@redhat.com> writes: > >>> > >>>> On Tue, Mar 07, 2023 at 11:04:33AM +0000, David Edmondson wrote: > >>>>> "Michael S. Tsirkin" <mst@redhat.com> writes: > >>>>> > +The driver MAY block use of VIRTIO_ADMIN_CMD_LIST_QUERY and > >>>>> > +VIRTIO_ADMIN_CMD_LIST_USE by issuing VIRTIO_ADMIN_CMD_LIST_USE > >>>>> > +with respective bits cleared in \field{command_specific_data}. > >>>>> > >>>>> This runs contrary to the assertion "The list of supported commands MUST > >>>>> NOT shrink", given that a driver is told to assume that > >>>>> VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_USE are the only > >>>>> commands initially available. > >>>> > >>>> Commands are still available just disabled, the meaning of > >>>> "MUST NOT shrink" is clarified by the following: > >>>> > >>>> > > +after reporting a given command as supported through > >>>> > > +VIRTIO_ADMIN_CMD_LIST_QUERY the device MUST NOT later report it > >>>> > > +as unsupported. > >>>> I will stick an "i.e." there to make it hopefully clearer. > >>> > >>>This puzzles me. > >>> > >>>I can see the point of blocking LIST_USE, but not of blocking > >> > >> What is that point, I'm curious. > > > >I might restrict the commands permitted by a device before handing it > >off to some subordinate less trusted code. > > Hmm, that is theoretical, or is there a usecase for that? > Maybe there will be a future version replacing VIRTIO_ADMIN_CMD_LIST_QUERY with a different command. Then we start with a device supporting both VIRTIO_ADMIN_CMD_LIST_QUERY and the new VIRTIO_ADMIN_FOO, and we block VIRTIO_ADMIN_CMD_LIST_QUERY for testing, to make sure driver is able to handle future devices without VIRTIO_ADMIN_CMD_LIST_QUERY. > > > >> > >>>LIST_QUERY. What's the purpose of this? > >> > >> I think that this might be just for the sake of treating all > >> commands equally. > >> > >> > >>>-- > >>>Time is waiting to explain, why refuse? > >>> > >>> --------------------------------------------------------------------- > >>>To unsubscribe from this mail list, you must leave the OASIS TC that > >>>generates this mail. Follow this link to all your TCs in OASIS at: > >>>https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > >>> > >-- > >I used to get mad at my school, the teachers who taught me weren't cool.