virtio — archive

[PATCH] virtio-pci: access device using config

From: Paolo Bonzini <[email protected]>
To: [email protected]
Date: Tue, 05 Nov 2013 09:51:00 -0000

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. Paolo