Bug 594546

Summary: [Intel 5.6 Bug] CPU synchronization required when doing MTRR register update
Product: Red Hat Enterprise Linux 5 Reporter: Don Dugger <ddugger>
Component: kernel-xenAssignee: Don Dugger <ddugger>
Status: CLOSED ERRATA QA Contact: chen yuwen <yuchen>
Severity: medium Docs Contact:
Priority: low    
Version: 5.6CC: ddugger, drjones, gasmith, jane.lv, jlv, jvillalo, knoel, ltroan, luyu, martin.wilck, mjenner, qcai, rpacheco, tao, xen-maint
Target Milestone: rc   
Target Release: 5.6   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: 594545 Environment:
Last Closed: 2011-01-13 21:33:24 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 514489, 557597, 576676    
Attachments:
Description Flags
Hypervisor patch none

Description Don Dugger 2010-05-21 01:09:38 UTC 
+++ This bug was initially created as a clone of Bug #594545 +++

Description of problem:
(Just as the kernel suffers from this problem so does the Xen hypervisor.)

Starting from Westmere, VMX transitions with cr0.cd=1 don't work properly (because of some VMX performance optimizations) and the scenario where one logical cpu is doing VMX activity and another logical cpu coming online can result in system crash.

Fortunately, the only time that cr0.cd is set to one is during MTRR updates so the kernel needs to bring all CPUs to a rendezvous, do the MTRR update and then resume all the CPUs.

The upstream Linux kernel has solved this problem with the patch:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d0af9eed5aa91b6b7b5049cae69e5ea956fd85c3

so this patch set needs to be back ported to the RHEL 5.6 kernel.
Comment 1 RHEL Program Management 2010-05-21 11:41:29 UTC 
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
release.
Comment 2 Don Dugger 2010-05-26 21:26:28 UTC 
About the bug description, the Xen patches are actually at:

http://xenbits.xensource.com/xen-unstable.hg?rev/cd46b418d171
Comment 3 Don Dugger 2010-05-28 02:26:41 UTC 
Created attachment 417442 [details]
Hypervisor patch

This is the actual Xen hypervisor patch that needs to be backported.
Comment 5 Jarod Wilson 2010-08-13 02:24:04 UTC 
in kernel-2.6.18-212.el5
You can download this test kernel from http://people.redhat.com/jwilson/el5

Detailed testing feedback is always welcomed.
Comment 8 chen yuwen 2010-12-31 06:14:50 UTC 
Confirmed patch in kernel 2.6.18-212.el5.
Setting SanityOnly.
Comment 10 errata-xmlrpc 2011-01-13 21:33:24 UTC 
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 therefore 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.

http://rhn.redhat.com/errata/RHSA-2011-0017.html