On Tue, May 12, 2026, at 5:12 PM, Michael S. Tsirkin wrote:
> On Tue, May 12, 2026 at 05:06:50PM -0600, Alex Williamson wrote:
>> If we agree that homogeneous hierarchies (no mixing of EA and
>> programmable BARs) is a reasonable constraint, and possibly extend that
>> to homogeneous per host bridge to simplify the CRS mapping, we have the
>> following work items:
>> 
>>  * Extend Linux EA support to program bridge apertures for subordinate
>>    homogeneous EA hierarchies.
>> 
>>  * Develop options to virtualize programmable BARs as EA for vfio-pci
>>    devices, if not generically for the benefit of testing.
>> 
>>  * Implement a way to poke holes in the VM address space and plumb
>>    through to account for addresses used by EA devices.
>> 
>>  * Provide those same ranges to the guest via CRS (but not via DT to
>>    EDK2), or alternatively expose them through additional PXB host
>>    bridges.
>> 
>> Does that shape roughly seem accurate?  Are there additional gaps I've
>> missed?  Thanks,
>
> just one question why not do it in firmware so windows
> is thinkably also handled?

I suppose someone could chime in if they have a similar requirement for Windows 
guests.  Otherwise, the incremental effort to extend Linux EA support seems 
smaller, though I also don't know what, if any support Windows has for EA to 
bother.  Regardless, improving Linux EA support might help elsewhere and 
doesn't preclude edk2 support in the future.  Thanks,

Alex


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