Re: [Xen-devel] how can native driver response quickly for low FIFO device

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 25 May 2006, at 10:11, Dong, Eddie wrote:

>         For those devices like UART which has very few FIFOs and no DMA
> support, how can scheduler (sedf?) help us to improve the response of
> native device driver in driver domain? Otherwise the receive data may 
> be
> overwritten in driver domain and then makes the device unusable.
You can have a receive FIFO as big as you like: it doesn't need to be 
visible to the HVM guest. If the guest has configured the UART with an 
'N-byte FIFO' then allocate the FIFO as big as you like and drive the 
UART device model logic such that if you have more than N bytes 
currently in the FIFO it looks to the guest (and the core of the device 
model) as if there are exactly N bytes currently in the FIFO.
 -- Keir


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