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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.
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Created attachment 505997 [details] [RHEL6.2 Xen PATCH] Mask dangerous features when running as xen guest hvm V2
Created attachment 506055 [details] [RHEL6.2 Xen PATCH V2] Mask dangerous features when running as xen guest hvm
Patch(es) available on kernel-2.6.32-165.el6
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.
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