Re: [kvm-unit-tests PATCH v4 07/12] arm: pmu: Basic event counter Tests

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Hi Eric,

A few comments when looking through the PMU test code (2 years after
the series was merged).

On 2020/4/3 15:13, Eric Auger wrote:
Adds the following tests:
- event-counter-config: test event counter configuration
- basic-event-count:
  - programs counters #0 and #1 to count 2 required events
  (resp. CPU_CYCLES and INST_RETIRED). Counter #0 is preset
  to a value close enough to the 32b
  overflow limit so that we check the overflow bit is set
  after the execution of the asm loop.
- mem-access: counts MEM_ACCESS event on counters #0 and #1
  with and without 32-bit overflow.

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>

[...]

diff --git a/arm/pmu.c b/arm/pmu.c
index 8c49e50..45dccf7 100644
--- a/arm/pmu.c
+++ b/arm/pmu.c
@@ -38,6 +43,7 @@
 #define SW_INCR			0x0
 #define INST_RETIRED		0x8
 #define CPU_CYCLES		0x11
+#define MEM_ACCESS		0x13
 #define INST_PREC		0x1B

The spec spells event 0x001B as INST_SPEC.

 #define STALL_FRONTEND		0x23
 #define STALL_BACKEND		0x24

[...]

@@ -175,6 +188,11 @@ static inline void precise_instrs_loop(int loop, uint32_t pmcr)
 }
#define PMCEID1_EL0 sys_reg(3, 3, 9, 12, 7)
+#define PMCNTENSET_EL0 sys_reg(3, 3, 9, 12, 1)
+#define PMCNTENCLR_EL0 sys_reg(3, 3, 9, 12, 2)
+
+#define PMEVTYPER_EXCLUDE_EL1 BIT(31)

Unused macro.

+#define PMEVTYPER_EXCLUDE_EL0 BIT(30)
static bool is_event_supported(uint32_t n, bool warn)
 {
@@ -228,6 +246,224 @@ static void test_event_introspection(void)
 	report(required_events, "Check required events are implemented");
 }
+/*
+ * Extra instructions inserted by the compiler would be difficult to compensate
+ * for, so hand assemble everything between, and including, the PMCR accesses
+ * to start and stop counting. isb instructions are inserted to make sure
+ * pmccntr read after this function returns the exact instructions executed
+ * in the controlled block. Loads @loop times the data at @address into x9.
+ */
+static void mem_access_loop(void *addr, int loop, uint32_t pmcr)
+{
+asm volatile(
+	"       msr     pmcr_el0, %[pmcr]\n"
+	"       isb\n"
+	"       mov     x10, %[loop]\n"
+	"1:     sub     x10, x10, #1\n"
+	"       ldr	x9, [%[addr]]\n"
+	"       cmp     x10, #0x0\n"
+	"       b.gt    1b\n"
+	"       msr     pmcr_el0, xzr\n"
+	"       isb\n"
+	:
+	: [addr] "r" (addr), [pmcr] "r" (pmcr), [loop] "r" (loop)
+	: "x9", "x10", "cc");
+}
+
+static void pmu_reset(void)
+{
+	/* reset all counters, counting disabled at PMCR level*/
+	set_pmcr(pmu.pmcr_ro | PMU_PMCR_LC | PMU_PMCR_C | PMU_PMCR_P);
+	/* Disable all counters */
+	write_sysreg_s(ALL_SET, PMCNTENCLR_EL0);
+	/* clear overflow reg */
+	write_sysreg(ALL_SET, pmovsclr_el0);
+	/* disable overflow interrupts on all counters */
+	write_sysreg(ALL_SET, pmintenclr_el1);
+	isb();
+}
+
+static void test_event_counter_config(void)
+{
+	int i;
+
+	if (!pmu.nb_implemented_counters) {
+		report_skip("No event counter, skip ...");
+		return;
+	}
+
+	pmu_reset();
+
+	/*
+	 * Test setting through PMESELR/PMXEVTYPER and PMEVTYPERn read,

s/PMESELR/PMSELR/ ?

+	 * select counter 0
+	 */
+	write_sysreg(1, PMSELR_EL0);
+	/* program this counter to count unsupported event */
+	write_sysreg(0xEA, PMXEVTYPER_EL0);
+	write_sysreg(0xdeadbeef, PMXEVCNTR_EL0);
+	report((read_regn_el0(pmevtyper, 1) & 0xFFF) == 0xEA,
+		"PMESELR/PMXEVTYPER/PMEVTYPERn");

Ditto

+	report((read_regn_el0(pmevcntr, 1) == 0xdeadbeef),
+		"PMESELR/PMXEVCNTR/PMEVCNTRn");

Ditto

+
+	/* try to configure an unsupported event within the range [0x0, 0x3F] */
+	for (i = 0; i <= 0x3F; i++) {
+		if (!is_event_supported(i, false))
+			break;
+	}
+	if (i > 0x3F) {
+		report_skip("pmevtyper: all events within [0x0, 0x3F] are supported");
+		return;
+	}
+
+	/* select counter 0 */
+	write_sysreg(0, PMSELR_EL0);
+	/* program this counter to count unsupported event */

We get the unsupported event number *i* but don't program it into
PMXEVTYPER_EL0 (or PMEVTYPER0_EL0). Is it intentional?

+	write_sysreg(i, PMXEVCNTR_EL0);
+	/* read the counter value */
+	read_sysreg(PMXEVCNTR_EL0);
+	report(read_sysreg(PMXEVCNTR_EL0) == i,
+		"read of a counter programmed with unsupported event");
+
+}

[...]

+
+static void test_mem_access(void)
+{
+	void *addr = malloc(PAGE_SIZE);

*addr* isn't freed at the end of test_mem_access(). The same in
test_chain_promotion() and test_overflow_interrupt().

Zenghui



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