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