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Tue, 29 Sep 2026 15:04:12 -0700 (PDT) Date: Tue, 29 Sep 2026 22:04:11 +0000 Mime-Version: 1.0 X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260929220411.3756519-1-coltonlewis@google.com> Subject: [PATCH] KVM: arm64: Check ID_AA64DFR0_EL1.PMUVer in reset_pmevtyper() From: Colton Lewis To: kvmarm@lists.linux.dev Cc: Marc Zyngier , Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Colton Lewis Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260929_150414_894304_D8ED8F93 X-CRM114-Status: GOOD ( 13.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org When userspace initializes a vCPU with KVM_ARM_VCPU_PMU_V3 but sets ID_AA64DFR0_EL1.PMUVer to NI (0) or IMP_DEF (0xf, which is sanitized to NI), resetting the vCPU invokes reset_pmevtyper(). Because reset_pmevtyper() only checks kvm_vcpu_has_pmu(), it proceeds to call kvm_pmu_evtyper_mask(), which reads PMUVer == 0 from ID_AA64DFR0_EL1 and triggers a WARN_ONCE("Unknown PMU version 0") in __kvm_pmu_event_mask(). Check ID_AA64DFR0_EL1.PMUVer directly in reset_pmevtyper() via kvm_has_feat() instead of kvm_vcpu_has_pmu() so that PMEVTYPER_EL0 resets to 0 without querying the event mask when PMUv3 is not exposed to the guest. Fixes: bc512d6a9b92 ("KVM: arm64: Make PMEVTYPER_EL0.NSH RES0 if EL2 isn't advertised") Suggested-by: Oliver Upton Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Colton Lewis --- arch/arm64/kvm/sys_regs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index a2f4e769a4282..0bb3c2f10a22c 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1060,7 +1060,7 @@ static u64 reset_pmevcntr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) static u64 reset_pmevtyper(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) { /* This thing will UNDEF, who cares about the reset value? */ - if (!kvm_vcpu_has_pmu(vcpu)) + if (!kvm_has_feat(vcpu->kvm, ID_AA64DFR0_EL1, PMUVer, IMP)) return 0; reset_unknown(vcpu, r); -- 2.56.0.rc1.315.gc6ed9934b7-goog