| Message ID | 1444153766-12532-3-git-send-email-cov@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Oct 06, 2015 at 01:49:25PM -0400, Christopher Covington wrote: > Ensure that reads of the PMCCNTR_EL0 are monotonically increasing, > even for the smallest delta of two subsequent reads. > > Signed-off-by: Christopher Covington <cov@codeaurora.org> > --- > arm/pmu.c | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/arm/pmu.c b/arm/pmu.c > index 91a3688..589e605 100644 > --- a/arm/pmu.c > +++ b/arm/pmu.c > @@ -33,6 +33,8 @@ struct pmu_data { > }; > }; > > +static const int samples = 10; #define NR_SAMPLES 10 > + > /* As a simple sanity check on the PMCR_EL0, ensure the implementer field isn't > * null. Also print out a couple other interesting fields for diagnostic > * purposes. For example, as of fall 2015, QEMU TCG mode doesn't implement > @@ -56,11 +58,38 @@ static bool check_pmcr(void) > return false; > } > > +/* Ensure that the cycle counter progresses between back-to-back reads. > + */ style nit: your block quotes don't have opening wing (the preferred kernel style - and, fwiw, my preference too...) > +static bool check_cycles_increase(void) > +{ > + struct pmu_data pmcr; > + > + pmcr.enable = 1; > + asm volatile("msr pmcr_el0, %0" : : "r" (pmcr)); > + > + for (int i = 0; i < samples; i++) { > + int a, b; > + > + asm volatile( > + "mrs %[a], pmccntr_el0\n" > + "mrs %[b], pmccntr_el0\n" > + : [a] "=r" (a), [b] "=r" (b)); > + > + if (a >= b) { > + printf("Read %d then %d.\n", a, b); > + return false; > + } > + } > + > + return true; > +} > + > int main(void) > { > report_prefix_push("pmu"); > > report("Control register", check_pmcr()); > + report("Monotonically increasing cycle count", check_cycles_increase()); > > return report_summary(); > } > -- > Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arm/pmu.c b/arm/pmu.c index 91a3688..589e605 100644 --- a/arm/pmu.c +++ b/arm/pmu.c @@ -33,6 +33,8 @@ struct pmu_data { }; }; +static const int samples = 10; + /* As a simple sanity check on the PMCR_EL0, ensure the implementer field isn't * null. Also print out a couple other interesting fields for diagnostic * purposes. For example, as of fall 2015, QEMU TCG mode doesn't implement @@ -56,11 +58,38 @@ static bool check_pmcr(void) return false; } +/* Ensure that the cycle counter progresses between back-to-back reads. + */ +static bool check_cycles_increase(void) +{ + struct pmu_data pmcr; + + pmcr.enable = 1; + asm volatile("msr pmcr_el0, %0" : : "r" (pmcr)); + + for (int i = 0; i < samples; i++) { + int a, b; + + asm volatile( + "mrs %[a], pmccntr_el0\n" + "mrs %[b], pmccntr_el0\n" + : [a] "=r" (a), [b] "=r" (b)); + + if (a >= b) { + printf("Read %d then %d.\n", a, b); + return false; + } + } + + return true; +} + int main(void) { report_prefix_push("pmu"); report("Control register", check_pmcr()); + report("Monotonically increasing cycle count", check_cycles_increase()); return report_summary(); }
Ensure that reads of the PMCCNTR_EL0 are monotonically increasing, even for the smallest delta of two subsequent reads. Signed-off-by: Christopher Covington <cov@codeaurora.org> --- arm/pmu.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)