On Thu, Nov 30, 2017 at 04:39:46PM +0000, Will Deacon wrote: > When running with the kernel unmapped whilst at EL0, the virtually-addressed > SPE buffer is also unmapped, which can lead to buffer faults if userspace > profiling is enabled. > > This patch prohibits SPE profiling of userspace when > arm_kernel_unmapped_at_el0(). > > Signed-off-by: Will Deacon <will.dea...@arm.com> > --- > drivers/perf/arm_spe_pmu.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c > index 8ce262fc2561..c028db8973a4 100644 > --- a/drivers/perf/arm_spe_pmu.c > +++ b/drivers/perf/arm_spe_pmu.c > @@ -675,6 +675,13 @@ static int arm_spe_pmu_event_init(struct perf_event > *event) > return -EOPNOTSUPP; > > /* > + * If kernelspace is unmapped when running at EL0, then the SPE > + * buffer will fault and prematurely terminate the AUX session. > + */ > + if (arm64_kernel_unmapped_at_el0() && !attr->exclude_user) > + dev_warn_once(&spe_pmu->pdev->dev, "unable to write to > profiling buffer from EL0. Try passing \"kaiser=off\" on the kernel command > line");
The commit messages sats this prohibits profiling, but we simply log a message. I take it you meant to return an error code, too? Thanks, Mark.
