Commit 1b92e65f authored by Oliver Upton's avatar Oliver Upton
Browse files

KVM: arm64: Provide 1 event counter on IMPDEF hardware 



PMUv3 requires that all programmable event counters are capable of
counting any event. The Apple M* PMU is quite a bit different, and
events have affinities for particular PMCs.

Expose 1 event counter on IMPDEF hardware, allowing the guest to do
something useful with its PMU while also upholding the requirements of
the architecture.

Tested-by: default avatarJanne Grunau <j@jannau.net>
Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250305203021.428366-1-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 2d00cab8

arch/arm64/kvm/pmu-emul.c

+7 −0
Original line number Diff line number Diff line
@@ -1038,6 +1038,13 @@ u8 kvm_arm_pmu_get_max_counters(struct kvm *kvm) 
{

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



	/*

	 * PMUv3 requires that all event counters are capable of counting any

	 * event, though the same may not be true of non-PMUv3 hardware.

	 */

	if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))

		return 1;



	/*

	 * The arm_pmu->cntr_mask considers the fixed counter(s) as well.

	 * Ignore those and return only the general-purpose counters.