Red Hat Bugzilla – Bug 218822
PAE 4GB bug in hypervisor when using HVM guests with > 4 GB ram
Last modified: 2007-11-30 17:07:38 EST
Description of problem:
See upstream changeset 12732. The following is a note about it from Tim Deegan:
> changeset: 12732:7df4d8cfba3b2fbd12ac1f287ab854ff4b242721
> user: Tim Deegan <Tim.Deegan@xensource.com>
> date: Tue Dec 05 12:42:29 2006 +0000
> files: xen/arch/x86/mm/shadow/common.c
> [XEN] sh_gfn_to_mfn_foreign() must handle guest pfns above 4GB on PAE
> Signed-off-by: Tim Deegan <Tim.Deegan@xensource.com>
> And wondered if you had any further information about the problems we'd see
> without this patch. Would it simply be psuedo-random crashes of the guest,
> or would the HV itself crash ? And is there any easy way to reproduce the
> problem for testing
For translated PAE guests on PAE hosts, where the guest has more than
4GB of RAM, you would see memory corruption within the guest, but not
Xen crashes. Since without Intel's map-cache patch we can't start HVM
guests with more than 2GB of RAM on PAE anyway, it's not been a problem.
The Intel developers working on the map-cache patch reported it; I don't
know what particular symptoms they were seeing.
Potentially this could cause memory corruption in translated-mode PV
guests (i.e. paravirt-ops kernels) with more than 4GB of RAM; I've not
been testing that case.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release. Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products. This request is not yet committed for inclusion in an Update
Switching to MODIFIED since we got the patch in changeset 12732 for free as part
of the 3.1 hypervisor/qemu rebase.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.