Re: [virtio] Re: [virtio-comment] [PATCH v10 09/10] admin: conformance clauses

[Jiri Pirko <jiri@nvidia.com>]

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?


>
>>
>>>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?
>>>
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>-- 
>I used to get mad at my school, the teachers who taught me weren't cool.