Re: [Qemu-devel] [PATCH 0/5][RFC] virtio-net: MAC filtering

Anthony Liguori
2009-01-09T19:41:13Z

Paul Brook wrote:
>> A concern here is the growing size of the virtio-net I/O port space
>> config. This series brings it up to 256 bytes with PCI resource
>> rounding. The VLAN filter bitmap would increase that by another 512
>> bytes, making it 1kB and limiting us to something less than 64 such
>> devices per guest. Is anyone worried? Should filter tables live in
>> MMIO space for virtio devices? I'll send out the guest side patches for
>> virtio-net in a separate thread. Thanks,
>>
>
> This is one reason why IO ports are a reallybad idea. Use memory mapped
> register spaces like any other sane system and you won't have a problem.
>

IO ports are much faster for notification than MMIO in KVM which is why
the space is currently IO ports. It was never meant to hold very large
amounts of data.

Regards,

Anthony Liguori

> Paul
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