From: Marc Zyngier maz@kernel.org
[ Upstream commit c8823e51b534d490ec27d372596eb35d2bb7193c ]
The MDCR_EL2 documentation indicates that the HPMN field has the following behaviour:
"On a Warm reset, this field resets to the expression NUM_PMU_COUNTERS."
However, it appears we reset it to zero, which is not very useful.
Add a reset helper for MDCR_EL2, and handle the case where userspace changes the target PMU, which may force us to change HPMN again.
Reported-by: Joey Gouly joey.gouly@arm.com Reviewed-by: Oliver Upton oliver.upton@linux.dev Signed-off-by: Marc Zyngier maz@kernel.org Stable-dep-of: c6e35dff58d3 ("KVM: arm64: Check for SYSREGS_ON_CPU before accessing the CPU state") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kvm/pmu-emul.c | 20 +++++++++++++++++++- arch/arm64/kvm/sys_regs.c | 8 +++++++- 2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index 60b5a5e4a6c5..2df54508f5ae 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@ -1027,12 +1027,30 @@ u8 kvm_arm_pmu_get_max_counters(struct kvm *kvm) return bitmap_weight(arm_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS); }
+static void kvm_arm_set_nr_counters(struct kvm *kvm, unsigned int nr) +{ + kvm->arch.nr_pmu_counters = nr; + + /* Reset MDCR_EL2.HPMN behind the vcpus' back... */ + if (test_bit(KVM_ARM_VCPU_HAS_EL2, kvm->arch.vcpu_features)) { + struct kvm_vcpu *vcpu; + unsigned long i; + + kvm_for_each_vcpu(i, vcpu, kvm) { + u64 val = __vcpu_sys_reg(vcpu, MDCR_EL2); + val &= ~MDCR_EL2_HPMN; + val |= FIELD_PREP(MDCR_EL2_HPMN, kvm->arch.nr_pmu_counters); + __vcpu_sys_reg(vcpu, MDCR_EL2) = val; + } + } +} + static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu) { lockdep_assert_held(&kvm->arch.config_lock);
kvm->arch.arm_pmu = arm_pmu; - kvm->arch.nr_pmu_counters = kvm_arm_pmu_get_max_counters(kvm); + kvm_arm_set_nr_counters(kvm, kvm_arm_pmu_get_max_counters(kvm)); }
/** diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 554490360ff6..c1e900a66d35 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2704,6 +2704,12 @@ static int set_imp_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, .set_user = set_imp_id_reg, \ .reset = reset_imp_id_reg, \ .val = mask, \ + } + +static u64 reset_mdcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) +{ + __vcpu_sys_reg(vcpu, r->reg) = vcpu->kvm->arch.nr_pmu_counters; + return vcpu->kvm->arch.nr_pmu_counters; }
/* @@ -3249,7 +3255,7 @@ static const struct sys_reg_desc sys_reg_descs[] = { EL2_REG(SCTLR_EL2, access_rw, reset_val, SCTLR_EL2_RES1), EL2_REG(ACTLR_EL2, access_rw, reset_val, 0), EL2_REG_VNCR(HCR_EL2, reset_hcr, 0), - EL2_REG(MDCR_EL2, access_mdcr, reset_val, 0), + EL2_REG(MDCR_EL2, access_mdcr, reset_mdcr, 0), EL2_REG(CPTR_EL2, access_rw, reset_val, CPTR_NVHE_EL2_RES1), EL2_REG_VNCR(HSTR_EL2, reset_val, 0), EL2_REG_VNCR(HFGRTR_EL2, reset_val, 0),