lkml.org 
[lkml]   [2012]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
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.



\
 
 \ /
  Last update: 2012-03-15 15:31    [W:0.037 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site