linux-kernel - [PATCH v2] KVM: arm64: Skip the KVM pmu initialization when hyp is unavailable

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Message-Id: <20250324023450.109312-1-justin.he@arm.com>
Date: Mon, 24 Mar 2025 02:34:50 +0000
From: Jia He <justin.he@....com>
To: Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Cc: Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	linux-kernel@...r.kernel.org,
	Jia He <justin.he@....com>
Subject: [PATCH v2] KVM: arm64: Skip the KVM pmu initialization when hyp is unavailable

When Hyp mode is unavailable (e.g., the kernel boots from EL1), skip the
unnecessary KVM pmu initialization.

Signed-off-by: Jia He <justin.he@....com>
---
v2: 
 - Utilize is_hyp_mode_available() for improved accuracy when detecting the
 guest VM case, as it accounts for scenarios where the kernel boots from EL1.

 arch/arm64/kvm/pmu-emul.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 6c5950b9ceac..81b1a84ee1b3 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -779,6 +779,13 @@ void kvm_host_pmu_init(struct arm_pmu *pmu)
 {
 	struct arm_pmu_entry *entry;
 
+	/*
+	 * When Hyp mode is unavailable (e.g., the kernel boots from EL1),
+	 * skip the unnecessary KVM PMU initialization.
+	 */
+	if (!is_hyp_mode_available())
+		return;
+
 	/*
 	 * Check the sanitised PMU version for the system, as KVM does not
 	 * support implementations where PMUv3 exists on a subset of CPUs.
-- 
2.34.1