linux-kernel - [PATCH 13/18] KVM: arm64: Advertise PMUv3 if IMPDEF traps are present

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Message-Id: <20241217212048.3709204-14-oliver.upton@linux.dev>
Date: Tue, 17 Dec 2024 13:20:43 -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: [PATCH 13/18] KVM: arm64: Advertise PMUv3 if IMPDEF traps are present

Advertise a baseline PMUv3 implementation when running on hardware with
IMPDEF traps of the PMUv3 sysregs.

Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
 arch/arm64/kvm/pmu-emul.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 98690e53dc73..553d02a03877 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -1262,7 +1262,17 @@ u8 kvm_arm_pmu_get_pmuver_limit(void)
 	pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer,
 			       read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1));
 
-	/* Treat IMPLEMENTATION DEFINED functionality as unimplemented */
+	/*
+	 * Spoof a barebones PMUv3 implementation if the system supports IMPDEF
+	 * traps of the PMUv3 sysregs
+	 */
+	if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
+		return ID_AA64DFR0_EL1_PMUVer_IMP;
+
+	/*
+	 * Otherwise, treat IMPLEMENTATION DEFINED functionality as
+	 * unimplemented
+	 */
 	if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
 		return 0;
 
-- 
2.39.5