Hi,
We can't hard-wire the PCI_COMMAND_IO to 0 since virtio are(may be)
transitional devices that support both IO and MEM. Since the device supports
both modes is up to firmware/OS to choose a working mode. Once the mode is
chosen it is expected to update the command register accordingly. This is why
PCI spec has separate bits for IO/MEM . If we dig into virtio implementation we
may find that we don't care if both bits are on and we may also be able to fix
any potential problems.
If every byte is important for ipxe you may leave the patches out, consciously
creating an "unfriendly" driver (QEMU will create an io-region for that and
will have some 'if' statements with politically correct comments: "Some drivers
enable IO even if .." :) )
Bottom line, I would add the patches but definitely there are not a must.
I hope I helped,
Marcel
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