Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes: > On Mon, Jan 07, 2019 at 04:27:27PM +0000, Andrew Murray wrote: >> For drivers that do not support context exclusion let's advertise the >> PERF_PMU_CAP_NOEXCLUDE capability. This ensures that perf will >> prevent us from handling events where any exclusion flags are set. >> Let's also remove the now unnecessary check for exclusion flags. >> >> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx> >> --- >> arch/x86/events/amd/ibs.c | 13 +------------ >> arch/x86/events/amd/power.c | 10 ++-------- >> arch/x86/events/intel/cstate.c | 12 +++--------- >> arch/x86/events/intel/rapl.c | 9 ++------- >> arch/x86/events/intel/uncore_snb.c | 9 ++------- >> arch/x86/events/msr.c | 10 ++-------- >> 6 files changed, 12 insertions(+), 51 deletions(-) > > You (correctly) don't add CAP_NO_EXCLUDE to the main x86 pmu code, but > then you also don't check if it handles all the various exclude options > correctly/consistently. > > Now; I must admit that that is a bit of a maze, but I think we can at > least add exclude_idle and exclude_hv fails in there, nothing uses those > afaict. > > On the various exclude options; they are as follows (IIUC): > > - exclude_guest: we're a HV/host-kernel and we don't want the counter > to run when we run a guest context. > > - exclude_host: we're a HV/host-kernel and we don't want the counter > to run when we run in host context. > > - exclude_hv: we're a guest and don't want the counter to run in HV > context. > > Now, KVM always implies exclude_hv afaict (for guests) On Power it mostly does. There's some host code that can run in real mode (MMU off) and therefore doesn't do a full context switch out of the guest (including the PMU), so that's host code that is running while the guest PMCs are still counting. cheers
