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Description of problem: We have been using nested virtualization to test RHEV deployments. Typically we have a Fedora 23 host with nested virtualization enabled, which runs a hypervisor and engine. In turn we'll launch vm's in the RHEV environment (typically CFME at this time) A new feature in 4.4 is: "KVM: Nested virtualization now supports VPID (same as PCID but for vCPUs) which makes it quite a bit faster" With 4.4 I see the vpid feature when I cat /proc/cpuinfo on RHEV hypervisors installed. When booting 4.3 I do not see this feature in the guests. On 4.4 kernels we are unable to boot VM's under RHEV. VM's get in a bad state when trying to launch them and the hypervisor starts complaining about cpu soft lockups. If I add a modeprobe.d file with 'options kvm_intel vpid=0' and unload and load the module before attempting to launch a vm it runs fine. Version-Release number of selected component (if applicable): kernel-4.4.4-301.fc23.x86_64 How reproducible: Always Steps to Reproduce: 1. Install RHEV on a Fedora 23 host with nested kvm enabled 2. Try to boot a vm on the new rhev cluster Actual results: VM hangs trying to start. You'll probably see cpu soft lockups on the hypervisor after awhile Expected results: VM boots Additional info: Going back to 4.3 kernels seems to work, as does adding a modprobe.d file to disable vpid within the kvm-intel module.
One bit of clarification, the modprobe.d file to disable vpid would be created on the RHEV hypervisor, not the Fedora baremetal host.
From the kernel bugzilla, it looks like this is fixed by http://article.gmane.org/gmane.linux.kernel/2179954. I think my preference is for this to just come in through the regular stable release instead of pulling in the patches separately. Please correct me if I found the wrong patch set.
Yes, I built a custom kernel with Paolo's patches and it works to fix the problem. I'm not opposed to us waiting for it to hit a newer kernel.
*********** MASS BUG UPDATE ************** We apologize for the inconvenience. There is a large number of bugs to go through and several of them have gone stale. Due to this, we are doing a mass bug update across all of the Fedora 23 kernel bugs. Fedora 23 has now been rebased to 4.7.4-100.fc23. Please test this kernel update (or newer) and let us know if you issue has been resolved or if it is still present with the newer kernel. If you have moved on to Fedora 24 or 25, and are still experiencing this issue, please change the version to Fedora 24 or 25. If you experience different issues, please open a new bug report for those.
This is no longer an issue and this bug can be closed. Thanks!