Re: [Xen-devel] Re: [PATCH][RFC][IA64] Accelerate IDE PIO on HVM/IA64

[Alan <alan@xxxxxxxxxxxxxxxxxxx>]

On Tue, 5 Dec 2006 11:19:38 +0900
Kouya SHIMURA <kouya@xxxxxxxxxxxxxx> wrote:

> Hi, Tristan
> 
> Thanks for your comments.
> 
> * In any case, I have to allocate another page for IDE PIO buffer.
>   Actually this patch works well on any size of buffer. The size is
>   just trade-off with the performance. FYI, 2048 bytes seems to be
>   enough for CDROM.

You want a bit more if you ever begin to support multimedia or READ/WRITE
LONG, that can get you up to about 2500 bytes per "sector".

You also need to watch that you handle inb/inw/inl on the data port
properly as devices can support 32bit I/O on the data port which is not
the same as a 32bit I/O usually is (it does not return the value of port,
port +1, port + 2, port +3). Or you can report that 32bit I/O is not
supported in the drive identify page..

Alan

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