Re: [Qemu-devel] [virtio-dev] Re: [virtio-dev] Re: [PATCH RFC] virtio-net: enable configurable tx queue size

[Michael S. Tsirkin]

On Thu, May 25, 2017 at 08:13:31PM +0800, Jason Wang wrote:
> > 
> > The point of using the config field here is, when tomorrow's device is
> > released with a requirement for the driver
> > to use max_chain_size=1022 (not today's 1023), today's driver will
> > naturally support tomorrow's device without
> > any modification, since it reads the max_chain_size from the config
> > field which is filled by the device (either today's
> > device or tomorrow's device with different values).
> 
> I'm not saying anything wrong with the config filed you introduced. But you
> should answer the following question:
> 
> Is it useful to support more than 1024? If yes, why? If not, introduce a
> VIRTIO_F_SG_1024 is more than enough I think.
> 
> Thanks

I think it's useful to limit it below queue size too.

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MST