Re: [Fedora-ia64-list] kernel 2.6.16-1.2097_FC6 unbootable on Itanium

Jack Steiner
2006-03-30T15:49:07Z

On Thu, Mar 30, 2006 at 08:43:43AM -0700, David Mosberger-Tang wrote:
> On 3/30/06, Jack Steiner <steiner@sgi.com> wrote:
>
> > Is this problem unique to SN systems
>
> No, the same will happen on all other systems (that I know of).
>
> > The BIOS reports that most
> > memory ranges support both CACHED & UNCACHED references. I _think_
> > this is correct.
>
> That's correct. The map shows the ways the page *can* be mapped, not
> the way it *should* be mapped.
>
> It's strange that ACPI would prefer to use WC when WB mapping is
> possible. They definitely need to pick one way and stick with it
> though. As you say, mapping the same page with different cacheability
> is a no-no (and at least in theory, it should cause an MCA even on
> real hardware).

It does, at least on our chipset. If the chipset detects a simultaneous
UC & C reference, it generates a BUS error. It is surprising how
quickly this MCA occurs when we break the rules.

>
> --david
>
> --
> Mosberger Consulting LLC, http://www.mosberger-consulting.com/

--
Jack