[kvm-unit-tests PATCH v3 1/3] arm: pmu: Add missing isb()'s after sys register writing

[Ricardo Koller <ricarkol@google.com>]

There are various pmu tests that require an isb() between enabling
counting and the actual counting. This can lead to count registers
reporting less events than expected; the actual enabling happens after
some events have happened.  For example, some missing isb()'s in the
pmu-sw-incr test lead to the following errors on bare-metal:

	INFO: pmu: pmu-sw-incr: SW_INCR counter #0 has value 4294967280
	PASS: pmu: pmu-sw-incr: PWSYNC does not increment if PMCR.E is unset
	FAIL: pmu: pmu-sw-incr: counter #1 after + 100 SW_INCR
	FAIL: pmu: pmu-sw-incr: counter #0 after + 100 SW_INCR
	INFO: pmu: pmu-sw-incr: counter values after 100 SW_INCR #0=82 #1=98
	PASS: pmu: pmu-sw-incr: overflow on counter #0 after 100 SW_INCR
	SUMMARY: 4 tests, 2 unexpected failures

Add the missing isb()'s on all failing tests, plus some others that seem
required:
- after clearing the overflow signal in the IRQ handler to make spurious
  interrupts less likely.
- after direct writes to PMSWINC_EL0 for software to read the correct
  value for PMEVNCTR0_EL0 (from ARM DDI 0487H.a, page D13-5237).

Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 arm/pmu.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arm/pmu.c b/arm/pmu.c
index 15c542a2..4c601b05 100644
--- a/arm/pmu.c
+++ b/arm/pmu.c
@@ -307,6 +307,7 @@ static void irq_handler(struct pt_regs *regs)
 			}
 		}
 		write_sysreg(ALL_SET, pmovsclr_el0);
+		isb();
 	} else {
 		pmu_stats.unexpected = true;
 	}
@@ -534,10 +535,12 @@ static void test_sw_incr(void)
 	write_sysreg_s(0x3, PMCNTENSET_EL0);
 
 	write_regn_el0(pmevcntr, 0, PRE_OVERFLOW);
+	isb();
 
 	for (i = 0; i < 100; i++)
 		write_sysreg(0x1, pmswinc_el0);
 
+	isb();
 	report_info("SW_INCR counter #0 has value %ld", read_regn_el0(pmevcntr, 0));
 	report(read_regn_el0(pmevcntr, 0) == PRE_OVERFLOW,
 		"PWSYNC does not increment if PMCR.E is unset");
@@ -547,10 +550,12 @@ static void test_sw_incr(void)
 	write_regn_el0(pmevcntr, 0, PRE_OVERFLOW);
 	write_sysreg_s(0x3, PMCNTENSET_EL0);
 	set_pmcr(pmu.pmcr_ro | PMU_PMCR_E);
+	isb();
 
 	for (i = 0; i < 100; i++)
 		write_sysreg(0x3, pmswinc_el0);
 
+	isb();
 	report(read_regn_el0(pmevcntr, 0)  == 84, "counter #1 after + 100 SW_INCR");
 	report(read_regn_el0(pmevcntr, 1)  == 100,
 		"counter #0 after + 100 SW_INCR");
@@ -618,9 +623,12 @@ static void test_chained_sw_incr(void)
 
 	write_regn_el0(pmevcntr, 0, PRE_OVERFLOW);
 	set_pmcr(pmu.pmcr_ro | PMU_PMCR_E);
+	isb();
+
 	for (i = 0; i < 100; i++)
 		write_sysreg(0x1, pmswinc_el0);
 
+	isb();
 	report(!read_sysreg(pmovsclr_el0) && (read_regn_el0(pmevcntr, 1) == 1),
 		"no overflow and chain counter incremented after 100 SW_INCR/CHAIN");
 	report_info("overflow=0x%lx, #0=%ld #1=%ld", read_sysreg(pmovsclr_el0),
@@ -634,9 +642,12 @@ static void test_chained_sw_incr(void)
 	write_regn_el0(pmevcntr, 1, ALL_SET);
 	write_sysreg_s(0x3, PMCNTENSET_EL0);
 	set_pmcr(pmu.pmcr_ro | PMU_PMCR_E);
+	isb();
+
 	for (i = 0; i < 100; i++)
 		write_sysreg(0x1, pmswinc_el0);
 
+	isb();
 	report((read_sysreg(pmovsclr_el0) == 0x2) &&
 		(read_regn_el0(pmevcntr, 1) == 0) &&
 		(read_regn_el0(pmevcntr, 0) == 84),
@@ -821,10 +832,14 @@ static void test_overflow_interrupt(void)
 	report(expect_interrupts(0), "no overflow interrupt after preset");
 
 	set_pmcr(pmu.pmcr_ro | PMU_PMCR_E);
+	isb();
+
 	for (i = 0; i < 100; i++)
 		write_sysreg(0x2, pmswinc_el0);
 
+	isb();
 	set_pmcr(pmu.pmcr_ro);
+	isb();
 	report(expect_interrupts(0), "no overflow interrupt after counting");
 
 	/* enable interrupts */
@@ -879,6 +894,7 @@ static bool check_cycles_increase(void)
 	set_pmccfiltr(0); /* count cycles in EL0, EL1, but not EL2 */
 
 	set_pmcr(get_pmcr() | PMU_PMCR_LC | PMU_PMCR_C | PMU_PMCR_E);
+	isb();
 
 	for (int i = 0; i < NR_SAMPLES; i++) {
 		uint64_t a, b;
@@ -894,6 +910,7 @@ static bool check_cycles_increase(void)
 	}
 
 	set_pmcr(get_pmcr() & ~PMU_PMCR_E);
+	isb();
 
 	return success;
 }
-- 
2.37.1.559.g78731f0fdb-goog