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Bug 711317

Summary: Mask dangerous features on xen hvm, even if the HV doesn't
Product: Red Hat Enterprise Linux 6 Reporter: Igor Mammedov <imammedo>
Component: kernelAssignee: Igor Mammedov <imammedo>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: medium    
Version: 6.2CC: behoward, bsarathy, clalance, cmorgan, dhoward, drjones, fhrbata, jgreguske, kzhang, leiwang, lersek, pbonzini, qwan, sforsber, sghosh, tburke, whayutin, xen-maint, yugzhang
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: kernel-2.6.32-165.el6 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: 709856 Environment:
Last Closed: 2011-12-06 13:32:58 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: 709856    
Bug Blocks: 653816    
Attachments:
Description Flags
[RHEL6.2 Xen PATCH] Mask dangerous features when running as xen guest hvm V2
none
[RHEL6.2 Xen PATCH V2] Mask dangerous features when running as xen guest hvm none

Comment 2 Andrew Jones 2011-06-07 07:45:09 UTC 
We should defend xen hvm guests against any unforeseen issues with constant_tsc
and nonstop_tsc as well. This is lower priority than the xenpv guest fix
though, since analysis and testing hasn't yet found issues with hvm guests.
Comment 3 RHEL Program Management 2011-06-07 08:01:16 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 4 Igor Mammedov 2011-06-22 12:58:51 UTC 
Created attachment 505997 [details]
[RHEL6.2 Xen PATCH] Mask dangerous features when running as xen guest hvm V2
Comment 5 Igor Mammedov 2011-06-22 16:25:29 UTC 
Created attachment 506055 [details]
[RHEL6.2 Xen PATCH V2] Mask dangerous features when running as xen guest hvm
Comment 6 Aristeu Rozanski 2011-07-08 21:57:56 UTC 
Patch(es) available on kernel-2.6.32-165.el6
Comment 9 Qixiang Wan 2011-09-06 11:52:46 UTC 
Verified with kernel-2.6.32-193.el6.

Tested with:

[1] Host : Intel Quad CPU Q9400, kernel-xen-2.6.18-259.el5 (which hasn't mask some of the features like pdpe1gb in hypervisor).

Before fix : HVM guest with RHEL6.1 GA kernel

# cat /proc/cpuinfo
...
flags		: fpu tsc msr pae cx8 cmov pat pse36 clflush dts mmx fxsr sse sse2 ss ht pbe syscall nx lm constant_tsc up arch_perfmon pebs bts rep_good aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm tpr_shadow vnmi flexpriority

After fix: HVM guest with kernel-2.6.32-193.el6
# cat /proc/cpuinfo
...
flags		: fpu tsc msr pae cx8 cmov pat pse36 clflush dts mmx fxsr sse sse2 ss ht pbe syscall nx lm up arch_perfmon pebs bts rep_good aperfmperf pni dtes64 ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm dts tpr_shadow vnmi flexpriority
...

# dmesg
...
CPU: CPU feature constant_tsc disabled on xen guest
...

[2] Host: AMD Opteron(tm) Processor 6168,  kernel-xen-2.6.18-259.el5

RHEL6.1 HVM guest with kernel-2.6.32-193.el6:

# cat /proc/cpuinfo
...
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat clflush mmx fxsr sse sse2 syscall nx mmxext lm up rep_good extd_apicid unfair_spinlock pni cx16 hypervisor lahf_lm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt
...

# dmesg
...
CPU: CPU feature pdpe1gb disabled on xen guest
CPU: CPU feature rdtscp disabled on xen guest

So the features are masked in the guest after fix, change this bug to VERIFIED.
Comment 10 errata-xmlrpc 2011-12-06 13:32:58 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1530.html