Re: OVMF exposure in libvirt

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On 14.07.2014 16:12, Paolo Bonzini wrote:
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

And how should the FW cmd line look like then?


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.

Whoa. How to detect this? I mean, how do detect both?


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'.


Makes sense.

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.

I'm not big fan of this. Pre-creating storage is something that should be done by mgmt applications (migration with non-shared storage is something different).


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

Great. Do they work automagically or does libvirt need to enable the formatting somehow (e.g. monitor command, cmd line argument, ...)?


Paolo

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