Re: [PATCH] ACPI: bind workqueues to CPU 0 to avoid SMI corruption

[Bjorn Helgaas <bjorn.helgaas@hp.com>]

On Wednesday 29 July 2009 08:43:00 pm Shaohua Li wrote:
> On Thu, Jul 30, 2009 at 05:54:25AM +0800, Bjorn Helgaas wrote:
> > On some machines, a software-initiated SMI causes corruption unless the
> > SMI runs on CPU 0.  An SMI can be initiated by any AML, but typically it's
> > done in GPE-related methods that are run via workqueues, so we can avoid
> > the known corruption cases by binding the workqueues to CPU 0.
> > 
> > References:
> >     http://bugzilla.kernel.org/show_bug.cgi?id=13751
> >     https://bugs.launchpad.net/bugs/157171
> >     https://bugs.launchpad.net/bugs/157691
> Good job! Since any AML code can invoke a SMI, I wonder if all ACPICA should be
> limited to run on CPU 0?

I did look into doing that, but I didn't see an easy way to do it.

My first thought was that we could do a set_cpus_allowed() in
acpi_ex_enter_interpreter() and restore in acpi_ex_exit_interpreter().
But of course, those are ACPI CA functions, so to do it without an
ACPI CA change would mean some kind of hook in acpi_os_wait_semaphore(),
and there, we don't know *which* semaphore means "enter interpreter".

So I gave up for now.  But if somebody has a smarter idea, I agree
that it would be nice to at least have the option to run all AML on
CPU 0.

Bjorn