Re: [PATCH 15/15] Revert "x86: default to reboot via ACPI"

Ingo Molnar
2008-11-06T14:30:28Z

* Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Thu, Nov 06, 2008 at 08:14:45AM +0100, Ingo Molnar wrote:
> >
> > * Eduardo Habkost <ehabkost@redhat.com> wrote:
> >
> > > This reverts commit c7ffa6c26277b403920e2255d10df849bd613380.
> > >
> > > Now that we have the hooks to disable virtualization on
> > > emergency_restart(), we can get back to the BOOT_KBD reboot_type default.
> > >
> > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> >
> > hm, why revert this? There's nothing wrong with the ACPI reboot
> > method, it's just that we surprise the BIOS by exiting with an unclean
> > VMX state in certain circumstances.
> >
> > if the ACPI reboot method does not work we do the KBD method as the
> > next thing in the reboot chain.
>
> I suppose there are cases where the new default broke without KVM,
> and the suggestion was to disable VMX before rebooting instead of
> changing the default.
>
> Avi changed the default because on some machines reboot=kbd breaks
> when VMX is enabled, but the regressions caused by the new default
> doesn't necessarily involve VMX.

there's another reason as well: a growing quirk-list of machines where
ACPI is the best (sometimes only) method to reboot.

> Andrey Borzenkov's patch, for example, adds a new DMI entry because
> reboot=acpi breaks his keyboard (even without KVM, I guess). Andrey,
> was that the case?

hm, IIRC the problem was KVM in his case too.

Ingo