On 03/21/2013 08:19 AM, Michael S. Tsirkin wrote: >> >> In BIOS (e.g. SeaBIOS), using MMIO is very difficult, so your boot ROM >> probably wants to use I/O space even if MMIO is available. > > Is this a real concern? Modern cards seem to supply PXE ROMs even > though they have no IO BARs. > Most of them do really ugly hacks in hardware (like putting in a "back door" in config space) to make that possible. > > Problem is, BIOS and OS normally assume failure to allocate > any resources means card won't function and disable it. > So it does not seem to be worth it to have such a > device specific failover ability. > That is a violation of the PCIe spec; the PCIe spec specifically states that failure to allocate an I/O BAR should still allow the device to function. So we shouldn't rule it out going forward. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
