Commit 93b01528 authored by Oliver Upton's avatar Oliver Upton
Browse files

KVM: arm64: Compute PMCEID from arm_pmu's event bitmaps 



The PMUv3 driver populates a couple of bitmaps with the values of
PMCEID{0,1}, from which the guest's PMCEID{0,1} can be derived. This
is particularly convenient when virtualizing PMUv3 on IMP DEF hardware,
as reading the nonexistent PMCEID registers leads to a rather unpleasant
UNDEF.

Tested-by: default avatarJanne Grunau <j@jannau.net>
Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250305202641.428114-4-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 46573d94

arch/arm64/kvm/pmu-emul.c

+36 −11
Original line number Diff line number Diff line
@@ -842,22 +842,29 @@ static struct arm_pmu *kvm_pmu_probe_armpmu(void) 
	return pmu;

}



u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)

static u64 __compute_pmceid(struct arm_pmu *pmu, bool pmceid1)

{

	unsigned long *bmap = vcpu->kvm->arch.pmu_filter;

	u64 val, mask = 0;

	int base, i, nr_events;

	u32 hi[2], lo[2];



	if (!kvm_vcpu_has_pmu(vcpu))

		return 0;

	bitmap_to_arr32(lo, pmu->pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);

	bitmap_to_arr32(hi, pmu->pmceid_ext_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);



	return ((u64)hi[pmceid1] << 32) | lo[pmceid1];

}



static u64 compute_pmceid0(struct arm_pmu *pmu)

{

	u64 val = __compute_pmceid(pmu, 0);



	if (!pmceid1) {

		val = read_sysreg(pmceid0_el0);

	/* always support CHAIN */

	val |= BIT(ARMV8_PMUV3_PERFCTR_CHAIN);

		base = 0;

	} else {

		val = read_sysreg(pmceid1_el0);

	return val;

}



static u64 compute_pmceid1(struct arm_pmu *pmu)

{

	u64 val = __compute_pmceid(pmu, 1);



	/*

	 * Don't advertise STALL_SLOT*, as PMMIR_EL0 is handled

	 * as RAZ
@@ -865,6 +872,24 @@ u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1) 
	val &= ~(BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT - 32) |

		 BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT_FRONTEND - 32) |

		 BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT_BACKEND - 32));

	return val;

}



u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)

{

	struct arm_pmu *cpu_pmu = vcpu->kvm->arch.arm_pmu;

	unsigned long *bmap = vcpu->kvm->arch.pmu_filter;

	u64 val, mask = 0;

	int base, i, nr_events;



	if (!kvm_vcpu_has_pmu(vcpu))

		return 0;



	if (!pmceid1) {

		val = compute_pmceid0(cpu_pmu);

		base = 0;

	} else {

		val = compute_pmceid1(cpu_pmu);

		base = 32;

	}