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SubjectRe: [PATCH] EFI: Only set regions uncacheable if they support it
On 03/15/2012 07:33 AM, Matthew Garrett wrote:
>>
>> 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...
>
> We've already mapped it at this point - we then go back and flag it UC
> if it's not writeback. The latter seems to be causing problems, I'm not
> sure we've seen any indication that the former is. And these regions are
> marked as runtime accessible, so per spec they do need to be mapped into
> address space...
>

In other words, it's totally f*cked. I guess at that point mapping it
WB and letting the BIOS-configured MTRRs deal with the caching
attributes is probably the right thing to do.

I would still really like to understand why we're seeing #MCs... that's
bothersome all by itself.

-hpa


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