Messages in this thread Patch in this message | | | Date | Wed, 27 Sep 2023 08:02:40 +0000 | From | Oliver Upton <> | Subject | Re: [PATCH v6 02/11] KVM: arm64: PMU: Set the default PMU for the guest on vCPU reset |
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Hi Raghu,
On Tue, Sep 26, 2023 at 11:39:59PM +0000, Raghavendra Rao Ananta wrote: > From: Reiji Watanabe <reijiw@google.com> > > The following patches will use the number of counters information > from the arm_pmu and use this to set the PMCR.N for the guest > during vCPU reset. However, since the guest is not associated > with any arm_pmu until userspace configures the vPMU device > attributes, and a reset can happen before this event, call > kvm_arm_support_pmu_v3() just before doing the reset. > > No functional change intended.
I would argue there still is a functional change here, as PMU initialization failure now shows up on a completely different ioctl for userspace.
> @@ -216,6 +217,18 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) > vcpu->arch.reset_state.reset = false; > spin_unlock(&vcpu->arch.mp_state_lock); > > + if (kvm_vcpu_has_pmu(vcpu)) { > + if (!kvm_arm_support_pmu_v3()) > + return -EINVAL; > + > + /* > + * When the vCPU has a PMU, but no PMU is set for the guest > + * yet, set the default one. > + */ > + if (unlikely(!kvm->arch.arm_pmu) && kvm_arm_set_default_pmu(kvm)) > + return -EINVAL; > + } > +
Ah, this probably will not mix well with my recent change to get rid of the return value altogether from kvm_reset_vcpu() [*]. I see two ways to handle this:
- Add a separate helper responsible for one-time setup of the vCPU called from KVM_ARM_VCPU_INIT which may fail.
- Add a check for !kvm->arch.arm_pmu to kvm_arm_pmu_v3_init(). No strong preference, though.
[*]: https://lore.kernel.org/r/20230920195036.1169791-8-oliver.upton@linux.dev
-- Thanks, Oliver
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