Re: [edk2-devel] [PATCH v4 7/8] PciHostBridgeDxe: Extend service to get base addresses before allocation

["Ojeda Leon, Nicolas" <ncoleon@amazon.de>]

>> > Hmm, so you are hiding the #define here to avoid updating Protocol/PciHostBridgeResourceAllocation.h ...
>> >
>> > I suspect if this can't be implemented in the pci enumerator alone there is just no way around actually extending uefi protocols.  But it's also not fully clear to me why you need this new "partial" state.
>> > Wouldn't you know either nothing or both base + size for a resource?
>> >
>>
>> Yes you are right, the current status is we have nothing and after the 
>> resources are allocated we have base and size. However, the allocation 
>> happens after CreateResourceMap is called, this function is the one 
>> that iterates over all resources of all devices under a root bridges 
>> and places them in a root bridge relative offset to then calculate the 
>> length of the resources required for that specific root bridge. For 
>> the pre-populated BARs I retrieve the Base Address of the Root Bridge 
>> before placing the resources at the root bridge relative offset so 
>> that I can translate the BAR address (set by the host) into an offset.
>> That's why I created this patch to retrieve only the base address 
>> before the root bridge resource map is created, submitted and 
>> allocated.
>
>Hmm, nasty init order issue.  No good idea offhand.
>
>Have you tried to exclude the pre-populated BARs from the host bridge windows communicated to the edk2 pci core?  The pci enumerator should not create overlapping pci bar assignment then.  But it might very well be that this only shifts the problem to another place ...
>
>take care,
>  Gerd

Haven't tried that but we are working on a new approach that do not touches the protocol at all but instead profits from the retry loop already in place and, after an allocation round, verifies if the pre-populated BARs are in the correct place, otherwise tries again. Similar to what is currently done when the allocation fails due to not enough space. Also we are creating a routine that "adjusts" the resources by analyzing pre-populated BAR situation to decide which device to reject before trying again.

Expect a new revision soon.

Best regards,

Nicolas





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