linux-kernel - Re: [PATCH] EFI: Only set regions uncacheable if they support it

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Message-ID: <20120315145125.3e46586c@pyramind.ukuu.org.uk>
Date:	Thu, 15 Mar 2012 14:51:25 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, matt.fleming@...el.com
Subject: Re: [PATCH] EFI: Only set regions uncacheable if they support it

On Thu, 15 Mar 2012 14:42:36 +0000
Matthew Garrett <mjg@...hat.com> wrote:

> On Thu, Mar 15, 2012 at 07:36:46AM -0700, H. Peter Anvin wrote:
> 
> > I would still really like to understand why we're seeing #MCs... that's
> > bothersome all by itself.
> 
> The region is the legacy video RAM, so I can imagine there being 
> something magic about it.

Presumably by the point we are booting the firmware and our own early
activities mean the pages are already marked write-combine and in our CPU
caches somewhere. Is the current boot code flushing any legacy video
mappings from cache before it plays with the cachability ?

Alan
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