Messages in this thread | | | Date | Wed, 15 Feb 2017 14:37:21 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/2] perf/x86/intel/pt: Fail event creation if VMX operation is on |
| |
On Wed, Feb 15, 2017 at 03:05:10PM +0200, Alexander Shishkin wrote: > Peter Zijlstra <peterz@infradead.org> writes: > > > On Wed, Feb 15, 2017 at 10:34:58AM +0200, Alexander Shishkin wrote: > > > >> Well, we can't make the limitation go away. You'll still have to stop > >> kvms to get any 'meaningful' PT data. > > > > Why would you need to stop all VMs in order to get your !VM data? Sure, > > you get black holes where the VM runs, but we should be able to see > > everything else. > > No, what I mean is that if you run kvm prior to starting perf record, > which I assume is the case for acme, your entire session is a black > hole. The VMXON happens pretty early on, you can open /dev/kvm, > ioctl(KVM_CREATE_VM) on it and that will do a VMXON already.
kvm_intel has a vmm_exclusive parameter, if you set that to 0 is _should_ behave much better.
| |