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Message-Id: <20241217212338.3709556-1-oliver.upton@linux.dev>
Date: Tue, 17 Dec 2024 13:23:38 -0800
From: Oliver Upton <oliver.upton@...ux.dev>
To: kvmarm@...ts.linux.dev
Cc: Marc Zyngier <maz@...nel.org>,
Joey Gouly <joey.gouly@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
Mingwei Zhang <mizhang@...gle.com>,
Colton Lewis <coltonlewis@...gle.com>,
Raghavendra Rao Ananta <rananta@...gle.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org,
Oliver Upton <oliver.upton@...ux.dev>
Subject: [RFC PATCH 17/18] KVM: arm64: Provide 1 event counter on IMPDEF hardware
PMUv3 requires that all programmable event counters are capable of
counting any event. The Apple M* PMU is quite a bit different, and
events have affinities for particular PMCs.
Expose 1 event counter on IMPDEF hardware, allowing the guest to do
something useful with its PMU while also upholding the requirements of
the architecture.
Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
Jury is still out on whether we want to do this, which is why this patch
is RFC.
arch/arm64/kvm/pmu-emul.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 3803737cbf7c..8f96a34d3da5 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -1046,8 +1046,12 @@ u8 kvm_arm_pmu_get_max_counters(struct kvm *kvm)
{
struct arm_pmu *arm_pmu = kvm->arch.arm_pmu;
+ /*
+ * PMUv3 requires that all event counters are capable of counting any
+ * event, though the same may not be true of non-PMUv3 hardware.
+ */
if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
- return 0;
+ return 1;
/*
* The arm_pmu->cntr_mask considers the fixed counter(s) as well.
--
2.39.5
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