From: "H. Peter Anvin" <hpa@zytor.com>
To: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, matt.fleming@intel.com
Subject: Re: [PATCH] EFI: Only set regions uncacheable if they support it
Date: Thu, 15 Mar 2012 07:36:46 -0700 [thread overview]
Message-ID: <4F61FE7E.9060600@zytor.com> (raw)
In-Reply-To: <20120315143308.GA4382@srcf.ucam.org>
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
next prev parent reply other threads:[~2012-03-15 14:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 13:56 Matthew Garrett
2012-03-15 14:00 ` H. Peter Anvin
2012-03-15 14:07 ` Matthew Garrett
2012-03-15 14:17 ` H. Peter Anvin
2012-03-15 14:24 ` Matthew Garrett
2012-03-15 14:28 ` H. Peter Anvin
2012-03-15 14:33 ` Matthew Garrett
2012-03-15 14:36 ` H. Peter Anvin [this message]
2012-03-15 14:42 ` Matthew Garrett
2012-03-15 14:47 ` H. Peter Anvin
2012-03-15 14:54 ` Matthew Garrett
2012-03-15 14:51 ` Alan Cox
2012-03-15 14:54 ` Alan Cox
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