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.
Paolo
