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[PATCH requirements 0/7] virtio net new features requirements
>
From: Michael S. Tsirkin <[email protected]>
> Sent: Tuesday, June 6, 2023 6:42 PM
> > +## 3.6 Header data split for the receive virtqueue 1. The device
> > +should be able to DMA the packet header and data to two different
> > +
memory locations, this enables driver and networking stack to perform
> zero
> > +
copy to application buffer(s).
>
> what is header here? which layer?
>
Usually L2 to L4. To be defined further.
> > +2. The driver should be able to configure maximum header buffer size per
> > +
virtqueue.
> > +3. The header buffer to be in a physically contiguous memory per
> > +virtqueue
>
> this is a requirement why?
>
Because fetching individual buffer memory pointer is sub-optimal.
> > +4. The device should be able to indicate header data split in the receive
> > +
completion.
> > +5. The device should be able to zero pad the header buffer when the
> received
> > +
header is shorter than cpu cache line size.
>
> weirdly specific.
> how does device even know the cache line?
>
A driver can tell how much padding to be done by keeping the cache line specific details in the driver, but only telling about padding size.
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