On Tue, Oct 25, 2022, Bill Wendling wrote: > On Wed, Jun 1, 2022 at 10:22 AM Jim Mattson <jmattson@xxxxxxxxxx> wrote: > > > > On Wed, Jun 1, 2022 at 9:30 AM Bill Wendling <morbo@xxxxxxxxxx> wrote: > > > > > > From: Bill Wendling <isanbard@xxxxxxxxx> > > > > > > Clang can be more aggressive at inlining than GCC and will fully inline > > > calls to measure(). This can mess with the counter overflow check. To > > > set up the PMC overflow, check_counter_overflow() first records the > > > number of instructions retired in an invocation of measure() and checks > > > to see that subsequent calls to measure() retire the same number of > > > instructions. If inlining occurs, those numbers can be different and the > > > overflow test fails. > > > > > > FAIL: overflow: cntr-0 > > > PASS: overflow: status-0 > > > PASS: overflow: status clear-0 > > > PASS: overflow: irq-0 > > > FAIL: overflow: cntr-1 > > > PASS: overflow: status-1 > > > PASS: overflow: status clear-1 > > > PASS: overflow: irq-1 > > > FAIL: overflow: cntr-2 > > > PASS: overflow: status-2 > > > PASS: overflow: status clear-2 > > > PASS: overflow: irq-2 > > > FAIL: overflow: cntr-3 > > > PASS: overflow: status-3 > > > PASS: overflow: status clear-3 > > > PASS: overflow: irq-3 > > > > > > Disabling inlining of measure() keeps the assumption that all calls to > > > measure() retire the same number of instructions. > > > > > > Cc: Jim Mattson <jmattson@xxxxxxxxxx> > > > Signed-off-by: Bill Wendling <morbo@xxxxxxxxxx> > > Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx> > > Bumping for visibility. Heh, make sure kvm-unit-tests is in the subject, i.e. [kvm-unit-tests PATCH]. This slipped by on my end because I didn't realize at a quick glance that it was touching KVM-unit-tests and not kernel code.
