[PATCH 0/8] KVM: arm64: Disabled PMU handling

[Alexandru Elisei]

Hi Marc,

On 11/13/20 6:25 PM, Marc Zyngier wrote:
> It recently dawned on me that the way we handle PMU traps when the PMU
> is disabled is plain wrong. We consider that handling the registers as
> RAZ/WI is a fine thing to do, while the ARMv8 ARM is pretty clear that
> that's not OK and that such registers should UNDEF when FEAT_PMUv3
> doesn't exist. I went all the way back to the first public version of
> the spec, and it turns out we were *always* wrong.
>
> It probably comes from the fact that we used not to trap the ID
> registers, and thus were unable to advertise the lack of PMU, but
> that's hardly an excuse. So let's fix the damned thing.
>
> This series adds an extra check in the helpers that check for the
> validity of the PMU access (most of the registers have to checked
> against some enable flags and/or the accessing exception level), and
> rids us of the RAZ/WI behaviour.
>
> This enables us to make additional cleanups, to the point where we can
> remove the PMU "ready" state that always had very bizarre semantics.
> All in all, a negative diffstat, and spec compliant behaviours. What's
> not to like?
>
> I've run a few guests with and without PMUs as well as KUT, and
> nothing caught fire. The patches are on top of kvmarm/queue.
Everything looks fine to me. You can add my Reviewed-by tag the patches I haven't
commented on separately.

Thanks,

Alex

>
> Marc Zyngier (8):
>   KVM: arm64: Add kvm_vcpu_has_pmu() helper
>   KVM: arm64: Set ID_AA64DFR0_EL1.PMUVer to 0 when no PMU support
>   KVM: arm64: Refuse illegal KVM_ARM_VCPU_PMU_V3 at reset time
>   KVM: arm64: Inject UNDEF on PMU access when no PMU configured
>   KVM: arm64: Remove PMU RAZ/WI handling
>   KVM: arm64: Remove dead PMU sysreg decoding code
>   KVM: arm64: Gate kvm_pmu_update_state() on the PMU feature
>   KVM: arm64: Get rid of the PMU ready state
>
>  arch/arm64/include/asm/kvm_host.h |  3 ++
>  arch/arm64/kvm/pmu-emul.c         | 11 +++----
>  arch/arm64/kvm/reset.c            |  4 +++
>  arch/arm64/kvm/sys_regs.c         | 51 ++++++++-----------------------
>  include/kvm/arm_pmu.h             |  3 --
>  5 files changed, 24 insertions(+), 48 deletions(-)
>