Re: [Xen-devel] HVMlite ABI specification DRAFT A

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.02.16 at 12:30, <roger.pau@xxxxxxxxxx> wrote:
> El 5/2/16 a les 11:40, Jan Beulich ha escrit:
>>>>> On 05.02.16 at 10:50, <roger.pau@xxxxxxxxxx> wrote:
>>> For legacy PCI interrupts, we can parse the MADT inside of Xen in order
>>> to properly setup the lines/overwrites and inject the interrupts that
>>> are not handled by Xen straight into the hardware domain. This will
>>> require us to be able to emulate the same topology as what is found in
>>> native (eg: if there are two IO APICs in the hardware we should also
>>> provide two emulated ones to the hw domain).
>> 
>> I don't think MADT contains all the needed information, or else we
>> wouldn't need PHYSDEVOP_setup_gsi.
> 
> AFAICT, I think we could do something like:
> 
>  - IRQs [0, 15]: edge-trigger, low-polarity.
>  - IRQs [16, n]: level-triggered, high-polarity.

That's not a valid assumption - I've seen systems with other settings
on GSI >= 16 ...

> Unless there's an overwrite in the MADT.

... and iirc that was without any MADT override (but instead coming
from the DSDT/SSDT).

> I expect that Xen will already have some code to deal with this, since
> it's also used for regular PCI-passthrough.

This has little to do with pass-through - we first of all need to get
the host working correctly on its own.

Jan


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