[PATCH] virtio-pci: access device using config

Paolo Bonzini <> writes:
> Il 05/11/2013 07:27, Rusty Russell ha scritto: >> "Michael S. Tsirkin" <> writes: >>>
> VIRTIO-39. >> We can discuss this on the call, but I don't like this. >>  >> PXE boot style environments will have to handle memory bars for modern >> PCIE devices.  Why should virtio be special? >
> Many devices these days do have some kind of backdoor to the memory
> BARs, through either config space or an I/O BAR.  AHCI even standardizes
> its backdoor with a special PCI capability. >
> GPUs also have backdoors in order to support accesses to BARs from the
> VGA BIOS without knowing the allocation of the BARs.  Often the GPUs use
> a register in the VGA ports (0x3b0...0x3df) so that they can even access
> BARs correctly even if the OS has already accessed 0xcf8 but has not
> accessed 0xcfc yet.  Wow, I had no idea.  OK, let's offer this then...  Thanks, Rusty.