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

Rafael J. Wysocki
2008-11-08T22:27:52Z

On Friday, 7 of November 2008, Robert Hancock wrote:
> Matthew Garrett wrote:
> > On Fri, Nov 07, 2008 at 09:01:19AM +0800, Zhao Yakui wrote:
> >
> >> With the help of KVM I find that the windows will be rebooted by writing
> >> RESET_VALUE to RESET_REG I/O port if the RESET_REG_SUP bit is not
> >> zero(It indicates whether ACPI reboot is supported).
> >> IMO maybe the ACPI reboot is the first choice. If it can't, then it will
> >> fall back to other mode.
> >
> > Hmm. But we're seeing some machines that end up very confused if
> > rebooted via ACPI. I guess we need to run Vista on them to find out how
> > they behave. What OSI strings did your KVM setup expose? We know that
> > Windows changes behaviour under various circumstances depending on which
> > OS the firmware requests, so it's almost possible that this is another
> > of those cases.
>
> Given that Windows behavior, this patch seems suspicious:
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=8fd145917fb62368a9b80db59562c20576238f5a
>
> This patch ignores the RESET_REG_SUP flag and just tries using the reset
> register anyway if it thinks it's valid. So we may attempt ACPI reset on
> machines which don't indicate it's supported.
>
> The patch description mentioned that some machines didn't reboot after
> S3 suspend without this patch. However, we recently had this patch merged:
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a68823ee5285e65b51ceb96f8b13a5b4f99a6888
>
> Is it possible that the problem fixed there is the true cause of this
> reboot after S3 problem?

Generally, it is.

Should it regarded as -stable material, BTW, or is it already in -stable?

Matthew?

Thanks,
Rafael