Re: [PATCH] fix reading from character devices

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Dor Laor wrote:
> On Mon, 2008-01-21 at 12:13 +0200, Avi Kivity wrote:
>   
>> Jan Kiszka wrote:
>>     
>>> Hi Avi,
>>>
>>> commit "kvm: qemu: consume all pending I/O in I/O loop"
>>> (8ab8bb09f1115b9bf733f885cc92b6c63d83f420) broke reading data bursts
>>> from serial devices (and maybe from other character devices as well) by
>>> guests. Reason: serial devices do input flow control via fd_read_poll,
>>> but qemu now ignores this fact by pushing all data into the virtual
>>> device as soon as it is available.
>>>
>>> Patch below is not really nice (just as the whole internal virtual I/O
>>> interface at the moment, IMHO), but it re-enables the serial ports for
>>> now.
>>>
>>>   
>>>       
>> I'm worried that it will break Dor's hack that speeds up virtio.  Dor?
>>
>>     
>
> It should be fine. Tap device without my hack has fd_read_poll null and
> I hacked it to have a handler that returns false if virtio is used and
> true otherwise. 
> So Jan's patch should set 'more' to 1 and it will be like before.
>
>   

But if virtio is used with this patch, it won't set 'more' to 1.  Will 
virtio handle it or will throughput drop to be related to whatever 
timers we have set up?

-- 
error compiling committee.c: too many arguments to function


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