From: Ian Campbell <Ian.Campbell@citrix.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Rzeszutek Wilk <konrad.wilk@oracle.com>,
Xen-devel <xen-devel@lists.xensource.com>,
Keir Fraser <Keir.Fraser@eu.citrix.com>,
Jan Beulich <JBeulich@novell.com>,
Konrad
Subject: Re: Xen's use of PAT and PV guests
Date: Tue, 30 Mar 2010 18:56:15 +0100 [thread overview]
Message-ID: <1269971775.2490.88.camel@localhost.localdomain> (raw)
In-Reply-To: <4BB1476D.4060209@goop.org>
On Tue, 2010-03-30 at 01:35 +0100, Jeremy Fitzhardinge wrote:
> It therefore seems to me that if I make Linux:
>
> 1. never set the PAT flag (which it won't anyway),
> 2. check that the value written to IA32_PAT is as expected, but
> otherwise ignore it, and
> 3. use WT rather than WC
>
> then it all should just work.
I had a patch ages ago (which I have now lost) that caused the kernel to
read back the PAT MSR after writing it and try and locate a suitable
entry for each cache setting it was interested in (with fallbacks as
appropriate) to use dynamically thereafter.
This has the nice property that Linux could write what it really wanted
to the PAT register but it would then read and use whatever it actually
ended up with.
I'm not sure that this scheme is at all upstreamable though.
Ian.
next prev parent reply other threads:[~2010-03-30 17:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-30 0:35 Xen's use of PAT and PV guests Jeremy Fitzhardinge
2010-03-30 7:44 ` Jan Beulich
2010-03-30 17:39 ` Jeremy Fitzhardinge
2010-03-30 17:59 ` Keir Fraser
2010-03-30 18:25 ` Jeremy Fitzhardinge
2010-03-30 16:57 ` Konrad Rzeszutek Wilk
2010-03-30 18:43 ` Jeremy Fitzhardinge
2010-03-31 8:26 ` Jan Beulich
2010-03-30 17:56 ` Ian Campbell [this message]
2010-03-30 21:47 ` Jeremy Fitzhardinge
2010-03-31 8:31 ` Ian Campbell
2010-03-31 16:55 ` Jeremy Fitzhardinge
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