On Wed, Mar 20, 2019 at 01:47:28PM -0700, Stephane Eranian wrote: > Right now, if I do: > > echo 0 > /sys/bus/event_source/devices/cpu/allow_tsx_force_abort > > Then I don't have the guarantee on when there will be no abort when I > return from the echo. the MSR is accessed only on PMU scheduling. I > would expect a sysadmin to want some guarantee if this is to be > switched on/off at runtime. If not, then having a boot time option is > better in my opinion.
Something like cycling the nmi watchdog or: perf stat -a -e cycles sleep 1 should be enough to force reschedule the events on every CPU. Again, I'm not adverse to 'fixing' this if it can be done with limited LoC. But I don't really see this as critical. > This other bit I noticed is that cpuc->tfa_shadow is used to avoid the > wrmsr(), but I don't see the code that makes sure the init value (0) > matches the value of the MSR. Is this MSR guarantee to be zero on > reset? That was my understanding. > How about on kexec()? Good point, we might want to fix that.
