linux-kernel - [PATCH 11/18] KVM: arm64: Move PMUVer filtering into KVM code

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Message-Id: <20241217212048.3709204-12-oliver.upton@linux.dev>
Date: Tue, 17 Dec 2024 13:20:41 -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 11/18] KVM: arm64: Move PMUVer filtering into KVM code

The supported guest PMU version on a particular platform is ultimately a
KVM decision. Move PMUVer filtering into KVM code.

Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
 arch/arm64/include/asm/cpufeature.h | 23 -----------------------
 arch/arm64/kvm/pmu-emul.c           | 15 +++++++++------
 2 files changed, 9 insertions(+), 29 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 6a989927926a..d49e9c7e201c 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -525,29 +525,6 @@ cpuid_feature_extract_unsigned_field(u64 features, int field)
 	return cpuid_feature_extract_unsigned_field_width(features, field, 4);
 }
 
-/*
- * Fields that identify the version of the Performance Monitors Extension do
- * not follow the standard ID scheme. See ARM DDI 0487E.a page D13-2825,
- * "Alternative ID scheme used for the Performance Monitors Extension version".
- */
-static inline u64 __attribute_const__
-cpuid_feature_cap_perfmon_field(u64 features, int field, u64 cap)
-{
-	u64 val = cpuid_feature_extract_unsigned_field(features, field);
-	u64 mask = GENMASK_ULL(field + 3, field);
-
-	/* Treat IMPLEMENTATION DEFINED functionality as unimplemented */
-	if (val == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
-		val = 0;
-
-	if (val > cap) {
-		features &= ~mask;
-		features |= (cap << field) & mask;
-	}
-
-	return features;
-}
-
 static inline u64 arm64_ftr_mask(const struct arm64_ftr_bits *ftrp)
 {
 	return (u64)GENMASK(ftrp->shift + ftrp->width - 1, ftrp->shift);
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 2c98cf24bef3..98690e53dc73 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -1257,13 +1257,16 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 
 u8 kvm_arm_pmu_get_pmuver_limit(void)
 {
-	u64 tmp;
+	unsigned int pmuver;
 
-	tmp = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
-	tmp = cpuid_feature_cap_perfmon_field(tmp,
-					      ID_AA64DFR0_EL1_PMUVer_SHIFT,
-					      ID_AA64DFR0_EL1_PMUVer_V3P5);
-	return FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), tmp);
+	pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer,
+			       read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1));
+
+	/* Treat IMPLEMENTATION DEFINED functionality as unimplemented */
+	if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
+		return 0;
+
+	return min(pmuver, ID_AA64DFR0_EL1_PMUVer_V3P5);
 }
 
 /**
-- 
2.39.5