On 23.05.14 07:01:41, Bjorn Helgaas wrote: > [I guess I've been using the wrong term here. I think "ECS" just > refers to the extended config space itself, and I should have been > saying "IO ECS" or "EnableCf8ExtCfg".] > > My understanding was that if we don't enable IO ECS and we don't have > MCFG, we will not be able to access extended config space. The system > can certainly boot without extended config space, but some drivers may > not work correctly, so it would be a regression from the user point of > view. No, I got you right. If we disable IO ECS there is no fallback if MCFG fails... and this may cause a regression then. I might be completely wrong here, but as I remember IO ECS only affects access to cpu devices (bus 0, slot 0x18-0x1f). Thus, esp. PCIe extended config space access works since a different host controller handles this. So only cpu devices would see a regression and thus cpu bringup code. I don't think ECS (either MCFG or IO ECS) is needed anymore for cpu bringup (this is true for IBS, but I don't know of other cpu features requiring ECS, though family 16h might introduced new ones). IMHO device drivers are not affected and wont get broken. -Robert -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
