Commit c8823e51 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: Fix MDCR_EL2.HPMN reset value 



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: default avatarJoey Gouly <joey.gouly@arm.com>
Reviewed-by: default avatarOliver Upton <oliver.upton@linux.dev>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent f12b54d7

arch/arm64/kvm/pmu-emul.c

+19 −1
Original line number Diff line number Diff line
@@ -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));

}



/**

arch/arm64/kvm/sys_regs.c

+7 −1
Original line number Diff line number Diff line
@@ -2700,6 +2700,12 @@ static int set_imp_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, 
	.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;

}



/*

 * Architected system registers.

 * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
@@ -3243,7 +3249,7 @@ 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),