Re: [virtio-comment] Re: [virtio-dev] Re: [virtio-comment] Re: [PATCH v7] virtio-net: support inner header hash

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

å 2023/1/10 äå3:26, Heng Qi åé:
> On Tue, Jan 10, 2023 at 12:57:38AM -0500, Michael S. Tsirkin wrote:
> > On Tue, Jan 10, 2023 at 12:25:02AM -0500, Michael S. Tsirkin wrote:
> > > > This will give extra pressure on the management stack, e.g it requires
> > > > the device to have an out of spec way for introspection.
> > > >
> > > > Thanks
> > > As I tried to explain this is already the case. Feature bits do not
> > > describe device capabilities fully, some of them are in config space.
> > To be precise, this does not necessarily require introspection, but
> > it does require management control over config space
> > such as supported hash types just like it has control over feature bits.
> > E.g. QEMU currently seems to hard-code these to
> > #define VIRTIO_NET_RSS_SUPPORTED_HASHES (VIRTIO_NET_RSS_HASH_TYPE_IPv4 | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_TCPv4 | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_IPv6 | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_TCPv6 | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_UDPv6 | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_IP_EX | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_TCP_EX | \
> >                                           VIRTIO_NET_RSS_HASH_TYPE_UDP_EX)
> >
> > but there's no reason not to give management control over these.
> Yes, QEMU has requirements for live migration: the PCI config space will be
> checked in get_pci_config_device(), and if src and dst are inconsistent, it
> will prompt that the live migration failed.

To be clearer, I mean \filed{supported_hash_types} in structure 
virtio_net_config.

Thanks.

> In fact, this is also done within our group. Live migration requires that
> the two VMs have the same rss configuration, otherwise the migration will fail.
>
> Therefore, it seems that we can regularize the description of VIRTIO_NET_F_HASH_TUNNEL into
> "[VIRTIO_NET_F_HASH_TUNNEL(52)] Device supports inner header hash for tunnel-encapsulated packets.",
> and use different hash_types to help the migration determine whether it can succeed.
>
> Thanks.
>
> > --
> > MST
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