4 messages in com.xensource.lists.xen-develRe: [Xen-devel] [PATCH] Limit MCG Cap
FromSent OnAttachments
Ben Guthro27 Aug 2007 12:11.patch
Keir Fraser28 Aug 2007 02:57 
David Lively28 Aug 2007 06:56 
David Lively29 Aug 2007 06:22.patch
Subject:Re: [Xen-devel] [PATCH] Limit MCG Cap
From:David Lively (dliv@virtualiron.com)
Date:08/29/2007 06:22:52 AM
List:com.xensource.lists.xen-devel
Attachments:

Hi Keir - Your suggestion to report 0 for reads of MSR_IA32_MCG_CAP seems to be working well on a wide variety of HVM guests (Windows & Linux, 32 & 64bit). I've attached a new patch.

Thanks, Dave

This patch implements a suggestion of Keir's (in response to a patch of mine):

Intercept guest reads of MSR_IA32_MCG_CAP and report 0, indicating no machine check "units", which agrees more closely with Xen's super-minimal machine check architecture (just enough to allow Windows to run).

This fixes a bug that occurs when migrating a RHEL4-64bit guest to a host with fewer machine check units than the original host. These host physical details shouldn't be leaking through to guests.

Signed-off-by: David Lively <dliv@virtualiron.com>

Keir Fraser wrote:

Given that we don't properly virtualise/emulate machine check (we only set the feature bit because some versions of Windows demand it) can we get away with returning zero for reads of MCG_CAP?

-- Keir

On 27/8/07 20:11, "Ben Guthro" <bgut@virtualiron.com> wrote:

Intercept guest reads of MSR_IA32_MCG_CAP and limit the number of memory banks reported to one. This prevents us from trying to read status of non-existent banks when migrated to a machine with fewer banks.