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    SubjectRe: [PATCH] EFI: Only set regions uncacheable if they support it
    On 03/15/2012 07:24 AM, Matthew Garrett wrote:
    > On Thu, Mar 15, 2012 at 07:17:56AM -0700, H. Peter Anvin wrote:
    >> On 03/15/2012 07:07 AM, Matthew Garrett wrote:
    >>>
    >>> 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".
    >>>
    >>
    >> In other words, "don't map me"... not something we really support at the
    >> moment, but perhaps we should; at least until we find systems in the
    >> field that break with that constraint :(
    >
    > Mapping should be harmless as long as we then don't touch it? I can't
    > think of any circumstances where we would.
    >

    If we map it WB software can do speculative loads from that region which
    would bring it into the cache. If we map it UC we might have to CLFLUSH...

    -hpa

    --
    H. Peter Anvin, Intel Open Source Technology Center
    I work for Intel. I don't speak on their behalf.



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