+ Shannon On 29/11/16 22:04, Itaru Kitayama wrote: > Hi, > > In a VM (virsh controlled, KVM acceleration enabled) on a recent > kvmarm kernel host, I find I am unable to use perf to obtain > performance statistics for a complex task like kernel build. > (I've verified this is seen with a Fedora 25 VM and host combination > as well) > APM folks CC'ed think this might be caused by a bug in the core PMU > framework code, thus I'd like to have experts opinion on this issue. > > [root@localhost linux]# perf stat -B make > CHK include/config/kernel.release > [ 119.617684] git[1144]: undefined instruction: pc=fffffc000808ff30 > [ 119.623040] Code: 51000442 92401042 d51b9ca2 d5033fdf (d53b9d40) > [ 119.627607] Internal error: undefined instruction: 0 [#1] SMP [...] In a VM running mainline hosted on an AMD Seattle box: Performance counter stats for 'make': 1526089.499304 task-clock:u (msec) # 0.932 CPUs utilized 0 context-switches:u # 0.000 K/sec 0 cpu-migrations:u # 0.000 K/sec 29527793 page-faults:u # 0.019 M/sec 2913174122673 cycles:u # 1.909 GHz 2365040892322 instructions:u # 0.81 insn per cycle <not supported> branches:u 32049215378 branch-misses:u # 0.00% of all branches 1637.531444837 seconds time elapsed Running the same host kernel on a Mustang system, the guest explodes in the way you reported. The failing instruction always seems to be an access to pmxevcntr_el0 (I've seen both reads and writes). Funnily enough, it dies if you try any HW event other than cycles ("perf stat -e cycles ls" works, and "perf stat -e instructions ls" explodes). Which would tend to indicate that we're screwing up the counter selection, but I have no proof of that (specially that the Seattle guest is working just as expected). Shannon, any idea? Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm