virtio — archive

[PATCH] virtio-pci: access device using config

From: Rusty Russell <[email protected]>
To: [email protected]
Date: Wed, 06 Nov 2013 02:17:00 -0000

Paolo Bonzini <[email protected]> writes: > Il 05/11/2013 07:27, Rusty Russell ha scritto: >> "Michael S. Tsirkin" <[email protected]> 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.