On 12.10.2021 12:06, Oleksandr Andrushchenko wrote: > On 12.10.21 13:01, Jan Beulich wrote: >> On 12.10.2021 11:38, Oleksandr Andrushchenko wrote: >>> On 12.10.21 12:32, Jan Beulich wrote: >>>> The minimal thing I'd suggest (or maybe you're doing this already) >>>> would be to expose such BARs to the guest as r/o zero, rather than >>>> letting their port nature "shine through". >>> If we have the same, but baremetal then which entity disallows >>> those BARs to shine? >> I'm sorry, but I don't understand what you're trying to say. >> >>> I mean that if guest wants to crash... why >>> should we stop it and try emulating something special for it? >> This isn't about a guest "wanting to crash", but a driver potentially >> getting mislead into thinking that it can driver a device a certain >> way. > Well, for the guest, as we do not advertise IO in the emulated host > bridge, the driver won't be able to allocate any IO at all. Thus, even > if we have a BAR with PCI_BASE_ADDRESS_SPACE_IO bit set, the > driver won't get anything. So, I think this is equivalent to a baremetal > use-case where we have no IO supported by the host bridge and > a device with IO BAR.
Oh, now I follow. Fair enough. Jan
