Hi Will, On Tue, Apr 25, 2017 at 10:23 PM, Will Deacon <will.dea...@arm.com> wrote: > On Tue, Apr 25, 2017 at 09:13:40AM +0530, Ganapatrao Kulkarni wrote: >> On Mon, Apr 24, 2017 at 9:15 PM, Will Deacon <will.dea...@arm.com> wrote: >> > On Thu, Apr 20, 2017 at 02:56:50PM +0530, Ganapatrao Kulkarni wrote: >> >> On Thu, Apr 20, 2017 at 2:19 PM, Mark Rutland <mark.rutl...@arm.com> >> >> wrote: >> >> > On Wed, Apr 19, 2017 at 11:14:06PM +0530, Ganapatrao Kulkarni wrote: >> >> >> commit d98ecda (arm64: perf: Count EL2 events if the kernel is running >> >> >> in HYP) >> >> >> is returning error for perf syscall with mixed attribute set for >> >> >> exclude_kernel >> >> >> and exclude_hv. This change is breaking some applications (observed >> >> >> with hhvm) >> >> >> when ran on VHE enabled platforms. >> >> >> >> >> >> Adding fix to consider only exclude_kernel attribute when kernel is >> >> >> running in HYP. Also adding sysfs file to notify the bhehaviour >> >> >> of attribute exclude_hv. >> >> >> >> >> >> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com> >> >> >> --- >> >> >> >> >> >> Changelog: >> >> >> >> >> >> V2: >> >> >> - Changes as per Will Deacon's suggestion. >> >> >> >> >> >> V1: Initial patch >> >> >> >> >> >> arch/arm64/kernel/perf_event.c | 28 ++++++++++++++++++++++++---- >> >> >> include/linux/perf/arm_pmu.h | 1 + >> >> >> 2 files changed, 25 insertions(+), 4 deletions(-) >> >> >> >> >> >> @@ -871,14 +890,13 @@ static int armv8pmu_set_event_filter(struct >> >> >> hw_perf_event *event, >> >> >> >> >> >> if (attr->exclude_idle) >> >> >> return -EPERM; >> >> >> - if (is_kernel_in_hyp_mode() && >> >> >> - attr->exclude_kernel != attr->exclude_hv) >> >> >> - return -EINVAL; >> >> >> + if (is_kernel_in_hyp_mode() && !attr->exclude_kernel) >> >> >> + config_base |= ARMV8_PMU_INCLUDE_EL2; >> >> >> if (attr->exclude_user) >> >> >> config_base |= ARMV8_PMU_EXCLUDE_EL0; >> >> >> if (!is_kernel_in_hyp_mode() && attr->exclude_kernel) >> >> >> config_base |= ARMV8_PMU_EXCLUDE_EL1; >> >> >> - if (!attr->exclude_hv) >> >> >> + if (!is_kernel_in_hyp_mode() && !attr->exclude_hv) >> >> >> config_base |= ARMV8_PMU_INCLUDE_EL2; >> >> > >> >> > This isn't quite what Will suggested. >> >> > >> >> > The idea was that userspace would read sysfs, then use that to determine >> >> > the correct exclusion parameters [1,2]. This logic was not expected to >> >> > change; it correctly validates whether we can provide what the user >> >> > requests. >> >> >> >> OK, if you are ok with sysfs part, i can send next version with that >> >> change only?. >> > >> > I think the sysfs part is still a little dodgy, since you still expose the >> > "exclude_hv" file with a value of 0 when not running at EL2, which would >> > imply that exclude_hv is forced to zero. I don't think that's correct. >> >> okay, i can make exclude_hv visible only when kernel booted in EL2. >> is it ok to have empty directory "attr" when kernel booted to EL1? >> attr can be place holder for any other miscellaneous attributes, that >> can be added in future. > > Sounds good to me, although I'll seek comment from the other perf folks > before merging anything with ABI implications.
Do you really think this is the solution given: - this is an arm64 specific sysfs interface that is tied to the perf API - the perf API documentation has to be updated for this - All the applications that use the perf API have to be modified to check this sysfs interface - If the application fails to do so, a very narrow corner case (exclude_hv != exclude_kernel and VHE enabled) fails. Any application that really cares can already do see if exclude_hv != exclude_kernel case works by calling perf_open_event() with those options and checking the return value. Hope I am mistake here, otherwise this does not sound like a good idea. JC.