[kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available

From: Marc Zyngier <maz@kernel.org>
To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Andrew Jones <drjones@redhat.com>,
	Eric Auger <eric.auger@redhat.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	qperret@google.com, kernel-team@android.com,
	Andrew Walbran <qwandor@google.com>
Subject: [kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available
Date: Wed, 24 Mar 2021 14:38:56 +0000	[thread overview]
Message-ID: <20210324143856.2079220-1-maz@kernel.org> (raw)

The PMU unit tests fail with an UNDEF exception when no PMU
is available (although KVM hasn't been totally consistent
with that in the past).

This is caused by PMCR_EL0 being read *before* ID_AA64DFR0_EL1
is checked for the PMU version.

Move the PMCR_EL0 access to a reasonable place, which allows the
test to soft-fail gracefully.

Fixes: 784ee933fa5f ("arm: pmu: Introduce defines for PMU versions")
Reported-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arm/pmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arm/pmu.c b/arm/pmu.c
index cc959e6..15c542a 100644
--- a/arm/pmu.c
+++ b/arm/pmu.c
@@ -988,7 +988,7 @@ static void pmccntr64_test(void)
 /* Return FALSE if no PMU found, otherwise return TRUE */
 static bool pmu_probe(void)
 {
-	uint32_t pmcr = get_pmcr();
+	uint32_t pmcr;
 	uint8_t implementer;
 
 	pmu.version = get_pmu_version();
@@ -997,6 +997,7 @@ static bool pmu_probe(void)
 
 	report_info("PMU version: 0x%x", pmu.version);
 
+	pmcr = get_pmcr();
 	implementer = (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK;
 	report_info("PMU implementer/ID code: %#"PRIx32"(\"%c\")/%#"PRIx32,
 		    (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK,
-- 
2.30.0

