[PATCH] KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status

[Raghavendra Rao Ananta <rananta@google.com>]

commit 54bbee190d42166209185d89070c58a343bf514b upstream.

DDI0487K.a D13.3.1 describes the PMU overflow condition, which evaluates
to true if any counter's global enable (PMCR_EL0.E), overflow flag
(PMOVSSET_EL0[n]), and interrupt enable (PMINTENSET_EL1[n]) are all 1.
Of note, this does not require a counter to be enabled
(i.e. PMCNTENSET_EL0[n] = 1) to generate an overflow.

Align kvm_pmu_overflow_status() with the reality of the architecture
and stop using PMCNTENSET_EL0 as part of the overflow condition. The
bug was discovered while running an SBSA PMU test [*], which only sets
PMCR.E, PMOVSSET<0>, PMINTENSET<0>, and expects an overflow interrupt.

Cc: stable@vger.kernel.org
Fixes: 76d883c4e640 ("arm64: KVM: Add access handler for PMOVSSET and PMOVSCLR register")
Link: https://github.com/ARM-software/sbsa-acs/blob/master/test_pool/pmu/operating_system/test_pmu001.c
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
[ oliver: massaged changelog ]
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241120005230.2335682-2-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 virt/kvm/arm/pmu.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 4c08fd009768..9732c5e0ed22 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -357,7 +357,6 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
 
 	if ((__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E)) {
 		reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
-		reg &= __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
 		reg &= __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
 		reg &= kvm_pmu_valid_counter_mask(vcpu);
 	}

base-commit: 6708005a36cfdb32aa991ebd9ea172e1183231ef
-- 
2.47.1.613.gc27f4b7a9f-goog