On Fri, 12 Mar 2021 at 09:16, Arnd Bergmann <a...@arndb.de> wrote: > So it's probably qemu that triggers the 'synchronous external > abort' when accessing the PCI I/O space, which in turn hints > towards a bug in qemu. Presumably it only returns data from > I/O ports that are actually mapped to a device when real hardware > is supposed to return 0xffffffff when reading from unused I/O ports.
Do you have a reference to the bit of the PCI spec that mandates this -1/discard behaviour for attempted access to places where there isn't actually a PCI device mapped ? The spec is pretty long and hard to read... (Knowing to what extent this behaviour is mandatory for all PCI systems/host controllers vs just "it would be nice if the gpex host controller worked this way" would help in figuring out where in QEMU to change.) thanks -- PMM
