Re: [virtio-comment] Re: [RFC PATCH v5 2/2] virtio-vsock: SOCK_SEQPACKET description

[Arseny Krasnov <arseny.krasnov@kaspersky.com>]

On 21.04.2021 12:54, Stefano Garzarella wrote:
> On Wed, Apr 21, 2021 at 04:24:36AM -0400, Michael S. Tsirkin wrote:
>> On Wed, Apr 21, 2021 at 09:45:23AM +0200, Stefano Garzarella wrote:
>>> On Wed, Apr 14, 2021 at 09:04:47AM +0300, Arseny Krasnov wrote:
>>>> On 13.04.2021 22:55, Michael S. Tsirkin wrote:
>>>>> On Tue, Apr 13, 2021 at 05:22:44PM +0300, Arseny Krasnov wrote:
>>>>>> On 13.04.2021 16:10, Michael S. Tsirkin wrote:
>>>>>>> On Tue, Apr 13, 2021 at 03:53:29PM +0300, Arseny Krasnov wrote:
>>>>>>>> This adds description of SOCK_SEQPACKET socket type
>>>>>>>> support for virtio-vsock.
>>>>>>>>
>>>>>>>> Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
>>>>>>>> ---
>>>>>>>>  virtio-vsock.tex | 26 +++++++++++++++++++++-----
>>>>>>>>  1 file changed, 21 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/virtio-vsock.tex b/virtio-vsock.tex
>>>>>>>> index ad57f9d..00e59cc 100644
>>>>>>>> --- a/virtio-vsock.tex
>>>>>>>> +++ b/virtio-vsock.tex
>>>>>>>> @@ -16,7 +16,10 @@ \subsection{Virtqueues}\label{sec:Device Types / Socket Device / Virtqueues}
>>>>>>>>
>>>>>>>>  \subsection{Feature bits}\label{sec:Device Types / Socket Device / Feature bits}
>>>>>>>>
>>>>>>>> -There are currently no feature bits defined for this device.
>>>>>>>> +\begin{description}
>>>>>>>> +\item VIRTIO_VSOCK_F_SEQPACKET (0) SOCK_SEQPACKET socket type is
>>>>>>>> +    supported.
>>>>>>> Does it make sense to only support seqpacket and not stream?
>>>>>>> I am guessing not since seqpacket is more or less
>>>>>>> a superset ...
>>>>>> You mean, this sentence must be "Both SOCK_SEQPACKET and SOCK_STREAM types
>>>>>>
>>>>>> are supported"?
>>>>> No. I am asking whether we want a feature bit for SOCK_STREAM too?
>>>> I think  there is no practical sense in SOCK_STREAM bit, because SOCK_SEQPACKET
>>>>
>>>> is stream + message boundaries and potential DGRAM is completely different
>>>>
>>>> thing. Of course i can implement it in my patches and also add it to spec patch, but  i see only
>>>>
>>>> esthetic in this: all three socket types have own feature bits.
>>>>
>>> I agree that it may make sense to have a bit for SOCK_STREAM. For example we
>>> may have devices in the future that want to implement only DGRAM for
>>> simplicity.
>>>
>>> I'm just worried about backwards compatibility with current devices where we
>>> don't have any feature bit.
>>>
>>> Should we add a negative feature flag? (e.g. VIRTIO_VSOCK_F_NO_STREAM)
>>> I don't like it much, but I can't think of anything better.
>>>
>>> Thanks,
>>> Stefano
>> We can simply specify that if there are no feature bits at all then
>> stream is assumed supported.
>>
> oh yeah, that sounds like a good idea!

So it is not necessary for my SEQPACKET patchset to support STREAM in both

kernel and spec?


Thank, Arseny

> Thanks,
> Stefano
>
>
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