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SubjectRe: [PATCH] EFI: Only set regions uncacheable if they support it
On Thu, Mar 15, 2012 at 07:00:06AM -0700, H. Peter Anvin wrote:
> On 03/15/2012 06:56 AM, Matthew Garrett wrote:
> > The EFI memory region attributes field indicates whether the region can
> > be mapped with various cache attributes. Our current implementation always
> > marks regions uncacheable if they don't have the writeback support flag.
> > This causes us to mark some regions uncacheable even if they don't
> > indicate support for being uncacheable, triggering a clflush that may cause
> > an MCE. Ensure we only do this for regions which support it.
> >
> > Signed-off-by: Matthew Garrett <mjg@redhat.com>
>
> Could you be specific as to what you're seeing in the field? In
> particular, what *do* these memory regions claim to support?

I have a report of a system that fails to boot with an MCE during EFI
setup. The memory range is marked reserved and claims not to support any
caching type, which I think probably translates as "Don't do anything to
this region ever".

--
Matthew Garrett | mjg59@srcf.ucam.org


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