[virtio-dev] Re: [virtio-comment] Re: [virtio-dev] [PATCH v8] virtio-net: correct conditions for devices to validate packet checksum

在 2024/1/12 上午12:27, Cornelia Huck 写道:
> On Thu, Jan 11 2024, Heng Qi <[email protected]> wrote:
>
>> 在 2024/1/4 下午12:47, Heng Qi 写道:
>>>
>>> 在 2024/1/3 下午2:35, Heng Qi 写道:
>>>> There is a historical error in virtio spec:
>>>>     "If VIRTIO_NET_F_GUEST_CSUM is not negotiated, the device *MUST*
>>>> set flags
>>>>      to zero and SHOULD supply a fully checksummed packet to the driver."
>>>>
>>>> Currently in Linux and virtio-related implementations, the device
>>>> validates
>>>> the packet checksum and sets DATA_VALID regardless of whether
>>>> VIRTIO_NET_F_GUEST_CSUM is negotiated.
>>>>
>>>> Please refer to the following summary and thread[1] for details and
>>>> reasons:
>>>>
>>>> Summary
>>>> =============
>>>> 1. GUEST_CSUM at virtio spec 0.95 is intended to be compatible with
>>>> partially
>>>> checksummed packets (NEEDS_CSUM <-> CHECKSUM_PARTIAL). So GUEST_CSUM
>>>> is mapped
>>>> to NETIF_F_RXCSUM.
>>>> GUEST_CSUM only indicates whether the driver handles partially
>>>> checksummed packets.
>>>> When XDP is loaded, the GUEST_CSUM's offload will be disabled, which
>>>> means that
>>>> packets have NEEDS_CSUM set will be dropped, and packets have
>>>> DATA_VALID set will
>>>> still be received.
>>>>
>>>> 2. When DATA_VALID was added to Linux in 2011[2] and virtio1.0, it
>>>> was actually
>>>> expected that rx checksum offload (the driver can set
>>>> CHECKSUM_UNNECESSARY) had
>>>> nothing to do with whether GUEST_CSUM was negotiated. But due to an
>>>> error, below
>>>> desctiption was added incorrectly:
>>>>     "If VIRTIO_NET_F_GUEST_CSUM is not negotiated, the device *MUST*
>>>> set flags
>>>>      to zero and SHOULD supply a fully checksummed packet to the driver."
>>>>
>>>> 3. We now hope to correct this error. Let the setting of DATA_VALID
>>>> not be
>>>> controlled by whether GUEST_CSUM is negotiated, but only controlled
>>>> by whether
>>>> rx checksum offload is enabled on the OS side. The state of this rx
>>>> checksum
>>>> offload is not aware of the device.
>>>>
>>>> 4. [Optional] NETIF_F_RXCSUM corresponding to rx checksum offload
>>>> should be
>>>> added to dev->hw_features. When the user turns off rx checksum
>>>> offload through
>>>> ethtool -K, neither NEEDS_CSUM nor DATA_VALID should be taken care
>>>> of, that is,
>>>> all packets will be marked as CHECKSUM_NONE.
>>>>
>>>> Related Link
>>>> =============
>>>> [1]
>>>> https://lists.oasis-open.org/archives/virtio-comment/202312/msg00135.html
>>>> [2] 10a8d94a9574 ("virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID")
>>>>
>>>> Fixes: https://github.com/oasis-tcs/virtio-spec/issues/185
>>> Hi Michael, Cornelia.
>>>
>>> Could you please open a voting for this fix?
>> Hi Michael and Cornelia.
>>
>> Sincerely asking if you missed this message?
> I've been back from end-of-year PTO only this week...
>
> I'm currently waiting for a confirmed updated schedule for the
> infrastructure migration, as I don't want to risk having the platform
> out of order in the middle of the voting period.

I got it. It depends on when the infrastructure is migrated, thanks for 
the sync.

>
>> In addition, Jason recently responded with his reviewed-by tag.
>> Do I need to publish a new version carrying his tag (thanks Jason)?
> No, we can add his R-b when pushing to git.

Ok.

Thanks.


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