** Description changed: SRU Justification: There has been an issue with older Xen hypervisors (Xen 3.x) which caused guest crashes with pv-ops kernels. For that we are carrying a patch borrowed from Fedora which masks off the OSXSAVE bit on CR4 writes. However there have been issues with that recently which were caused by user-space checking other flags and then trying to use the feature which then broke because it was not activated correctly. For Quantal we have now made the work-around patch better by not masking CR4 writes but actually removing the cpuid capability bits (and only for pre-4.x versions of Xen). This now needs to go back into previous releases. + + Update + ====== + It turned out that the hack (or the updated patch) are in fact only needed because Xen code in kernels between 2.6.30 and 2.6.39 would deliberately set OSXSAVE in CR4 in order to find out about xsave support. So any kernel newer that 2.6.39 can safely drop the work-around. And it should be done because having only OSXSAVE filtered on CR4 writes can cause problems and without any need we should not deviate from upstream. + + For Lucid we should either pick the patch which completely masks the + xsave bits from cpuid and optionally also the second patch that would + allow to use xsave when running as a guest of a Xen server supporting + it.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1044550 Title: Update the EC2 work-around for the OSXSAVE issue in pv-ops To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1044550/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
