On Thu, Dec 06, 2018 at 04:47:17PM +0000, Andrew Murray wrote: > Many PMU drivers do not have the capability to exclude counting events > that occur in specific contexts such as idle, kernel, guest, etc. These > drivers indicate this by returning an error in their event_init upon > testing the events attribute flags. > > However this approach requires that each time a new event modifier is > added to perf, all the perf drivers need to be modified to indicate that > they don't support the attribute. This results in additional boiler-plate > code common to many drivers that needs to be maintained. Furthermore the > drivers are not consistent with regards to the error value they return > when reporting unsupported attributes. > > This patchset allow PMU drivers to advertise their inability to exclude > based on context via a new capability: PERF_PMU_CAP_NO_EXCLUDE. This > allows the perf core to reject requests for exclusion events where there > is no support in the PMU. > > This is a functional change, in particular: > > - Some drivers will now additionally (but correctly) report unsupported > exclusion flags. It's typical for existing userspace tools such as > perf to handle such errors by retrying the system call without the > unsupported flags. > > - Drivers that do not support any exclusion that previously reported > -EPERM or -EOPNOTSUPP will now report -EINVAL - this is consistent > with the majority and results in userspace perf retrying without > exclusion. > > All drivers touched by this patchset have been compile tested. For the bits under arch/arm/ and drivers/perf: Acked-by: Will Deacon <will.deacon@xxxxxxx> Note that I've queued the TX2 uncore PMU for 4.21 [1], which could also benefit from your new flag. Will [1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=for-next/perf&id=69c32972d59388c041268e8206e8eb1acff29b9a
