[libvirt] OVMF exposure in libvirt

[Paolo Bonzini]

Il 14/07/2014 11:27, Daniel P. Berrange ha scritto:
>       -drive file=img_1,if=pflash,format=raw,readonly \
>       -drive file=img_2,if=pflash,format=raw

It's safer to add ",unit=0" and ",unit=1" too.

> We already use <loader/> for specifying alternative BIOS blobs for
> the QEMU -bios arg. Since you say this obsoletes the -bios arg, I
> think it makes sense to use <loader/> for the read-only firmware
> image.

It obsoletes the -bios argument, but it is not the same thing:

1) on some machines you can use "-drive if=pflash" for the nvram, but 
not for the firmware

2) on some older versions of QEMU, "-drive if=pflash" will work only on 
TCG or will not work at all so you cannot blindly replace it.

What about:

    <loader readonly='on|off' type='rom|flash'>...</loader>
    <nvram>...</nvram>

where the mapping from <nvram> to -drive if=flash is partly 
machine-dependent.  On x86, for example, <nvram> adds the ",unit=1" 
sub-option and fails if the <loader> element is absent; it also fails if 
<loader> has type='rom'.

> For the variable storage, I'd probably suggest <nvram/> as the
> element name, since IIUC that's a fairly commonly used term for
> this concept.

I like this.

> Additionally it would be great if we'd be able to
> generate an empty nvram for a guest if the user doesn't specify it.

Laszlo has OVMF patches to "auto-format" an all-zero nvram file.

Paolo