virtio — archive

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

? 2024/1/12 ??12:27, Cornelia Huck ??: > On Thu, Jan 11 2024, Heng Qi <hengqi@linux.alibaba.com> wrote: > >> ? 2024/1/4 ??12:47, Heng Qi ??: >>> >>> ? 2024/1/3 ??2:35, Heng Qi ??: >>>> 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.