[ipxe-devel] [ipxe/ipxe] virtio changes 5/2016 (#55)

Marcel Apfelbaum notifications at github.com
Tue Jun 21 08:49:17 UTC 2016

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,

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