From: Matthew Garrett <mjg@redhat.com>
To: Miles Fidelman <mfidelman@meetinghouse.net>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@redhat.com, hpa@zytor.com, x86@kernel.org,
peter.chubb@nicta.com.au, michael.d.labriola@gmail.com
Subject: Re: reboot via bios on X86_64?
Date: Mon, 9 Apr 2012 16:51:55 +0100 [thread overview]
Message-ID: <20120409155155.GA22974@srcf.ucam.org> (raw)
In-Reply-To: <4F8302B4.8040901@meetinghouse.net>
On Mon, Apr 09, 2012 at 11:39:32AM -0400, Miles Fidelman wrote:
> 1. What's the logic behind this? Why not enable a bios reboot for 64bit
> kernels? Is there any reason why the machine_real_restart code wouldn't
> work just as well in 64bit mode? Anybody know the history?
The bios reboot code requires you to reprogram the CPU to real mode. I
don't think there's any fundamental reason you can't do that from 64-bit
mode, but nobody's ever written that code.
> 2. Anybody know a workaround, short of patching and compiling a custom
> kernel? Are there other paths through the reboot code that can
> invoke a bios
> reboot? [Note: someone suggested trying a kexec-reboot, but that's also
> not supported on my configuration (running over a Xen hypervisor).]
Windows never uses the equivalent of the BIOS reboot method, so the
assumption is that if you ever need on Linux to it's because there's a
bug somewhere else. Does the platform reboot if you run the kernel on
bare metal rather than under Xen?
--
Matthew Garrett | mjg59@srcf.ucam.org
next prev parent reply other threads:[~2012-04-09 15:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-09 15:39 reboot via bios on X86_64? Miles Fidelman
2012-04-09 15:51 ` Matthew Garrett [this message]
2012-04-09 17:26 ` Miles Fidelman
2012-04-09 17:32 ` Matthew Garrett
2012-04-09 17:57 ` Miles Fidelman
2012-04-09 17:59 ` H. Peter Anvin
2012-04-09 18:06 ` Miles Fidelman
2012-04-09 18:07 ` Matthew Garrett
2012-04-10 14:03 ` Miles Fidelman
2012-04-10 14:22 ` Matthew Garrett
2012-04-10 17:26 ` Miles Fidelman
2012-04-10 17:44 ` Matthew Garrett
2012-04-10 18:09 ` Miles Fidelman
2012-04-09 17:53 ` H. Peter Anvin
2012-04-09 18:07 ` Miles Fidelman
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