linux-kernel - [RFC PATCH v4 18/39] KVM: arm64: Expose SPE version to guests

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Date:   Wed, 25 Aug 2021 17:17:54 +0100
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        will@...nel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 18/39] KVM: arm64: Expose SPE version to guests

Set the ID_AA64DFR0_EL1.PMSVer field to a non-zero value if the VCPU SPE
feature is set. SPE version is capped at FEAT_SPEv1p1 because KVM doesn't
yet implement freezing of PMU event counters on a SPE buffer management
event.

Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
---
 arch/arm64/kvm/sys_regs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index f6f126eb6ac1..ab7370b7a44b 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1070,8 +1070,10 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		val = cpuid_feature_cap_perfmon_field(val,
 						      ID_AA64DFR0_PMUVER_SHIFT,
 						      kvm_vcpu_has_pmu(vcpu) ? ID_AA64DFR0_PMUVER_8_4 : 0);
-		/* Hide SPE from guests */
-		val &= ~FEATURE(ID_AA64DFR0_PMSVER);
+		/* Limit guests to SPE for ARMv8.3 */
+		val = cpuid_feature_cap_perfmon_field(val,
+						      ID_AA64DFR0_PMSVER_SHIFT,
+						      kvm_vcpu_has_spe(vcpu) ? ID_AA64DFR0_PMSVER_8_3 : 0);
 		break;
 	case SYS_ID_DFR0_EL1:
 		/* Limit guests to PMUv3 for ARMv8.4 */
-- 
2.33.0