[libvirt] [RFC PATCH 1/2] qemu: Advertise ACPI support for aarch64 guests

[Daniel P. Berrange]

On Wed, Mar 08, 2017 at 04:56:30PM +0100, Andrea Bolognani wrote:
> So far, libvirt has assumed that only x86 supports ACPI,
> but that's inaccurate since aarch64 supports it too.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1429509
> ---
> Advertising ACPI support in capabilities means that tools
> such as virt-manager will start automatically adding the
> <acpi/> element for new guests.
> 
> However, existing guests are likely to lack that element
> and will suddenly lose ACPI capabilities: that could make
> them unbootable if the guest OS only supports booting via
> ACPI, which on the other hand is AFAIK not the case for
> current mainstream OSs.

Current Linux policy is to boot based on Device Tree, if both
Device Tree & ACPI are advertized to the guest. If we stop
advertizing ACPI for guests without <acpi/>, then QEMU would
only present Device Tree, which is what any Linux guest will
have already been using.

So while you're right that this is a semantic change, I think
it is reasonable to make this, as I expect the fallout to be
minimal, and it is easy to deal with by just adding <acpi/>
if it turned out to be a problem for specific guest OS types.


Regards,
Daniel
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