Re: [Xen-devel] [rfc 00/18] ioemu: use devfn instead of slots as the unit for passthrough

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 06/03/2009 06:55, "Yuji Shimada" <shimada-yxb@xxxxxxxxxxxxxxx> wrote:

>> I ask because Keir mentioned that one reason for not extending
>> the range is a worry that some HW won't be able to cope with that many GSI.
> 
> "version register" of APIC in ICH9 has "maximum redirection entries"
> field.  The field is equal to the number of interrupt input pins minus
> one and is in the range 0 through 239. So I think virtual GSI can be
> extended.
> 
> ICH9 datasheet: http://www.intel.com/assets/pdf/datasheet/316972.pdf
> 
> But I have not seen such big I/O APIC. So it is possible that guest OS
> can't handle big virtual I/O APIC.

I really think we should support sharing, and distributing devices
efficiently across devfn space. Then think about changes like this with
compatibility and versioning issues. But you know my position already!

 -- Keir



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