From: "H. Peter Anvin" <hpa@zytor.com>
To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Ian Campbell <Ian.Campbell@eu.citrix.com>,
Jeremy Fitzhardinge <jeremy@goop.org>,
the arch/x86 maintainers <x86@kernel.org>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Linux@zytor.com, "Pallipadi,
Venkatesh" <venkatesh.pallipadi@intel.com>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com>,
Xen-devel <xen-devel@lists.xensource.com>,
Jan Beulich <jbeulich@novell.com>, Ingo Molnar <mingo@elte.hu>,
Lu <yinghai@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@infradead.org>
Subject: Re: [Xen-devel] Re: [PATCH 06/16] xen: disable PAT
Date: Sat, 09 May 2009 11:36:25 -0700 [thread overview]
Message-ID: <4A05CD29.6050505@zytor.com> (raw)
In-Reply-To: <C62AF788.AAE1%keir.fraser@eu.citrix.com>
Keir Fraser wrote:
>
> My suggestion is that Xen changes its PAT[1] from WT to WC. AFAIK only
> suse's Linux port is currently using Xen's PAT support, and it does not
> actually use the WT cache attribute. Then Xen's PAT[0-3] would match what
> Linux expects, and Linux apparently does not risk using PAT[4-7] because of
> processor errata so their values are irrelevant. Linux can check that it is
> running on Xen with suitable PAT setup by reading MSR_IA32_CR_PAT and
> checking PAT[0-3], and only enable PAT usage in case of a match.
>
There exists at least one processor erratum where the CPU will use
PAT[4-7] when the user requested PAT[0-3]. For those CPUs, it is unsafe
for *any* OS to have PAT[4-7] != PAT[0-3].
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-05-09 18:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-07 21:10 [GIT PULL] xen: core dom0 support Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 01/16] xen dom0: Make hvc_xen console work for dom0 Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 02/16] xen dom0: Initialize xenbus " Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 03/16] xen dom0: Set up basic IO permissions " Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 04/16] xen dom0: Add support for the platform_ops hypercall Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 05/16] xen mtrr: Add mtrr_ops support for Xen mtrr Jeremy Fitzhardinge
2009-05-08 11:17 ` Ingo Molnar
2009-05-07 21:10 ` [PATCH 06/16] xen: disable PAT Jeremy Fitzhardinge
2009-05-08 11:14 ` Ingo Molnar
2009-05-08 12:38 ` Ian Campbell
2009-05-08 14:50 ` Alan Cox
2009-05-09 8:04 ` [Xen-devel] " Keir Fraser
2009-05-09 18:36 ` H. Peter Anvin [this message]
2009-05-10 9:21 ` Keir Fraser
2009-05-10 13:29 ` Alan Cox
2009-05-10 17:34 ` Keir Fraser
2009-05-10 17:55 ` H. Peter Anvin
2009-05-11 11:10 ` Ingo Molnar
2009-05-07 21:10 ` [PATCH 07/16] xen/dom0: use _PAGE_IOMAP in ioremap to do machine mappings Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 08/16] xen/dom0: Use host E820 map Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 09/16] xen: implement XENMEM_machphys_mapping Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 10/16] xen: clear reserved bits in l3 entries given in the initial pagetables Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 11/16] xen: allow enable use of VGA console on dom0 Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 12/16] xen/dom0: add XEN_DOM0 config option Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 13/16] x86: make /dev/mem mappings _PAGE_IOMAP Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 14/16] paravirtualize IO permission bitmap Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 15/16] x86: don't need "changed" parameter for set_io_bitmap() Jeremy Fitzhardinge
2009-05-07 21:10 ` [PATCH 16/16] xen: checkpatch cleanups Jeremy Fitzhardinge
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