On Tue, Aug 02, 2016 at 02:55:24PM +0200, Peter Zijlstra wrote: > On Tue, Aug 02, 2016 at 02:04:58PM +0200, Jiri Kosina wrote: > > With current Linus' tree (HEAD == 731c7d3a20), I am getting bogus MSR > > write warning during bootup, and kernel panic when shutting PMUs down > > during poweroff. > > > > The MSR warning is below, the camera capture of the poweroff panic can be > > found at > > > > http://www.jikos.cz/jikos/junk/pmu-panic.jpg > > > > The last previous kernel version that I've booted on this particular > > machine was 4.7.0-rc4, and it had neither of those symptoms, so I can > > eventually bisect if needed. > > > > === [ snip ] == > > [ 0.136000] smpboot: CPU0: Intel(R) Core(TM)2 Duo CPU L9400 @ > > 1.86GHz (family: 0x6, model: 0x17, stepping: 0x6) > > [ 0.136000] Performance Events: PEBS fmt0+, Core2 events, Intel PMU > > driver. > > [ 0.136000] ... version: 2 > > [ 0.136000] ... bit width: 40 > > [ 0.136000] ... generic registers: 2 > > [ 0.136000] ... value mask: 000000ffffffffff > > [ 0.136000] ... max period: 000000007fffffff > > [ 0.136000] ... fixed-purpose events: 3 > > [ 0.136000] ... event mask: 0000000700000003 > > [ 0.136000] NMI watchdog: enabled on all CPUs, permanently consumes one > > hw-PMU counter. > > [ 0.136000] unchecked MSR access error: WRMSR to 0xdf (tried to write > > 0x000000ff80000001) at rIP: 0xffffffff90004acc > > (x86_perf_event_set_period+0xdc/0x190) > > 'Curious'.. :/ > > x86_perf_event_set_period() only does: > > wrmsrl(hwc->event_base, (u64)(-left) & x86_pmu.cntval_mask); > > and hwc->event ends up being: > > MSR_ARCH_PERFMON_PERFCTR0 + index > > From which we can deduce that index = 0xdf - 0xc1 = 30, which is > somewhat larger than the max reported number of counters (2). > > Lemme go see how that can happen.
So I can reproduce on my Lenovo T500 which has a Core2 as well. By long and tedious printk() it looks like the event constraint: FIXED_EVENT_CONSTRAINT(0x003c, 1), /* CPU_CLK_UNHALTED.CORE */ which is updated in: intel_pmu_init() to include the generic counter masks, gets corrupted for some reason. But the moment I put printk()s in there to print the idxmsk64 values, everything works as expected again. I'll go prod mode.
