Re: [virtio-comment] Re: [PATCH v4 1/2] virtio-net: update description for VIRTIO_NET_F_GUEST_CSUM.

[Heng Qi <hengqi@linux.alibaba.com>]

在 2023/12/1 下午3:05, Jason Wang 写道:
> On Fri, Dec 1, 2023 at 2:30 PM Heng Qi <hengqi@linux.alibaba.com> wrote:
>>
>>
>> 在 2023/12/1 下午2:24, Heng Qi 写道:
>>>
>>> 在 2023/12/1 下午1:18, Jason Wang 写道:
>>>> On Wed, Nov 29, 2023 at 4:23 PM Heng Qi <hengqi@linux.alibaba.com>
>>>> wrote:
>>>>>
>>>>> 在 2023/11/29 下午4:00, Jason Wang 写道:
>>>>>> On Tue, Nov 28, 2023 at 4:08 PM Heng Qi <hengqi@linux.alibaba.com>
>>>>>> wrote:
>>>>>>> To prevent readers from misunderstanding that the driver can
>>>>>>> only handles packets with partial checksum when
>>>>>>> VIRTIO_NET_F_GUEST_CSUM is negotiated, we update the description.
>>>>>>>
>>>>>>> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
>>>>>>> ---
>>>>>>>     device-types/net/description.tex | 2 +-
>>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/device-types/net/description.tex
>>>>>>> b/device-types/net/description.tex
>>>>>>> index aff5e08..529f470 100644
>>>>>>> --- a/device-types/net/description.tex
>>>>>>> +++ b/device-types/net/description.tex
>>>>>>> @@ -38,7 +38,7 @@ \subsection{Feature bits}\label{sec:Device Types
>>>>>>> / Network Device / Feature bits
>>>>>>>     \begin{description}
>>>>>>>     \item[VIRTIO_NET_F_CSUM (0)] Device handles packets with
>>>>>>> partial checksum offload.
>>>>>>>
>>>>>>> -\item[VIRTIO_NET_F_GUEST_CSUM (1)] Driver handles packets with
>>>>>>> partial checksum.
>>>>>>> +\item[VIRTIO_NET_F_GUEST_CSUM (1)] Driver handles packets with
>>>>>>> partial checksum or full checksum.
>>>>>> So patch 2 said
>>>>>>
>>>>>> "
>>>>>> +\item[VIRTIO_NET_F_GUEST_FULL_CSUM (64)] Driver handles packets with
>>>>>> full checksum.
>>>>>>     \end{description}
>>>>>> "
>>>>>>
>>>>>> Is there any difference between the two "full checksum" here?
>>>>> There's no difference.
>>>>>
>>>>> The core is that VIRTIO_NET_F_GUEST_FULL_CSUM means that the driver
>>>>> "can
>>>>> only" handle packets with full checksum.
>>>> This seems to be odd.
>>>>
>>>> Driver can always handle packet with full checksum, no?
>>> Yes.
>>>
>>>> I meant it
>>>> will be then to be functional equivalent to !
>>>> VIRTIO_NET_F_GUEST_FULL_CSUM?
>>> Are you referring to
>>> "functional equivalent to !VIRTIO_NET_F_GUEST_CSUM" ?
>> Sorry, this is a typo. I meant
>>
>> Are you referring to
>> "functional equivalent to !VIRTIO_NET_F_GUEST_FULL_CSUM" ?
>>
>>> If so, I think it's no.
>>>
>>> Maybe a description similar to the following would be more clearer:
>>>
>>> +\item[VIRTIO_NET_F_GUEST_FULL_CSUM (64)] Driver does not handle
>>> packets with partial checksum.
> I may miss something here, but what's the difference between
>
> VIRTIO_NET_F_GUEST_FULL_CSUM
>
> and
>
> !VIRTIO_NET_F_GUEST_CSUM?

 From the device perspective:

If !VIRTIO_NET_F_GUEST_CSUM, the device delivers packets with full 
checksum to the driver,
but the device can not validate the checksum for these packets. That is, 
the flags in virtio-net-hdr
will not contain _DATA_VALID, and the driver or stack needs to validate 
these packets.

If VIRTIO_NET_F_GUEST_FULL_CSUM, the device delivers packets with full 
checksum to the driver,
and the device can validate the checksum for these packets. That is, the 
flags in virtio-net-hdr
will contain _DATA_VALID, and the driver or stack does not need to 
validate these packets.

Thanks!

>
> Thanks
>
>>> Thanks!
>>>
>>>> Thanks
>>>>
>>>>> Thanks!
>>>>>
>>>>>> Thanks
>>>>>>
>>>>>>> \item[VIRTIO_NET_F_CTRL_GUEST_OFFLOADS (2)] Control channel offloads
>>>>>>>             reconfiguration support.
>>>>>>> --
>>>>>>> 2.19.1.6.gb485710b
>>>>>>>
>>>
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