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

From: Jiri Pirko <jiri@nvidia.com>
To: David Edmondson <david.edmondson@oracle.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	virtio-comment@lists.oasis-open.org,
	virtio-dev@lists.oasis-open.org, jasowang@redhat.com,
	cohuck@redhat.com, sgarzare@redhat.com, stefanha@redhat.com,
	nrupal.jani@intel.com, Piotr.Uminski@intel.com,
	hang.yuan@intel.com, virtio@lists.oasis-open.org,
	Zhu Lingshan <lingshan.zhu@intel.com>,
	pasic@linux.ibm.com, Shahaf Shuler <shahafs@nvidia.com>,
	Parav Pandit <parav@nvidia.com>,
	Max Gurtovoy <mgurtovoy@nvidia.com>
Subject: [virtio-comment] Re: [virtio] Re: [virtio-comment] [PATCH v10 09/10] admin: conformance clauses
Date: Wed, 8 Mar 2023 15:02:05 +0100	[thread overview]
Message-ID: <ZAiVXdawwbZ8CvXR@nanopsycho> (raw)
In-Reply-To: <m21qlzz7br.fsf@oracle.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.

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