Re: [Qemu-devel] [RFC 0/4] virtio-mmio transport

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/09/2011 09:16 AM, Paul Brook wrote:
> [Replying to various bits of this thread all at once]
>
>>   * you have to specify which kind of virtio device you want in the
>>     board model. In particular this means that for virtio-blk the user
>>     has to say "-drive if=none,file=whatever.img,id=myimg
>>     -global virtio-blk-mmio.drive=myimg" or the virtio-blk layer will
>>     refuse to start, which is not at all userfriendly
>
> This is pretty lame.  I see two or three bugs here:
>
> 1) We're greating virtio devices unconditionally.  Much better would be to
> have devices be allocated as necessary.  e.g. unless the user explicitly
> requests otherwise, put the first device at a particular address, and
> subsequent devices at sequential addresses. The guest OS can then easily probe
> them to see which are present.  I guess a null virtio device might make sense
> to avoid accessing undefined memory regions.
> For the vexpress board the logic tile site (0xc0000000) seems like a sensible
> location.  Your current choice of an area reserved by the southbridge seems
> somewhat questionable.
>
> 2) virtio-blk fails if no drive is connected.  I guess you could call this a
> feature, which means you must fix (1).  If not then I think it's reasonable
> for hardcoded board devices should also use hardcoded drive IDs.  i.e. we act
> as if the user specified "-global virtio-blk-mmio.drive=virtio" or similar
>
> 3) "qemu -drive if=virtio" assmes you want PCI virtio.  Either we consider
> this an obsolete legacy option and document it as such, or fix it as part of
> (1).  In the latter case it's probably going to do the wrong thing on boards
> that have both virtio-mmio and PCI (there are at least two correct answers).
>
>> [...]
>> Correct.  Syborg virtio was something Paul Brook did bit is not an
>> "official" virtio transport as far as Linux or the spec is concerned.
>>
>> I'm not sure what guest software uses the syborg virtio transport.
>
> It is/was a virtual reference platform for SymbianOS.  However since then the
> Symbian Foundation got shot in the back of the head and the rest of Nokia
> jumped ship to Windows, so I'd be surprised if anyone really cares about it.

Can we remove syborg virtio then?

Regards,

Anthony Liguori

>
> Paul
>