On Wed, 10 Aug 2022 08:16:14 +0100,
Oliver Upton <oliver.upton@xxxxxxxxx> wrote:
>
> Hi Marc,
>
> On Fri, Aug 05, 2022 at 02:58:12PM +0100, Marc Zyngier wrote:
> > PMUv3p5 (which is mandatory with ARMv8.5) comes with some extra
> > features:
> >
> > - All counters are 64bit
> >
> > - The overflow point is controlled by the PMCR_EL0.LP bit
> >
> > Add the required checks in the helpers that control counter
> > width and overflow, as well as the sysreg handling for the LP
> > bit. A new kvm_pmu_is_3p5() helper makes it easy to spot the
> > PMUv3p5 specific handling.
> >
> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > ---
> > arch/arm64/kvm/pmu-emul.c | 8 +++++---
> > arch/arm64/kvm/sys_regs.c | 4 ++++
> > include/kvm/arm_pmu.h | 8 ++++++++
> > 3 files changed, 17 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
> > index 33a88ca7b7fd..b33a2953cbf6 100644
> > --- a/arch/arm64/kvm/pmu-emul.c
> > +++ b/arch/arm64/kvm/pmu-emul.c
> > @@ -50,13 +50,15 @@ static u32 kvm_pmu_event_mask(struct kvm *kvm)
> > */
> > static bool kvm_pmu_idx_is_64bit(struct kvm_vcpu *vcpu, u64 select_idx)
> > {
> > - return (select_idx == ARMV8_PMU_CYCLE_IDX);
> > + return (select_idx == ARMV8_PMU_CYCLE_IDX || kvm_pmu_is_3p5(vcpu));
> > }
> >
> > static bool kvm_pmu_idx_has_64bit_overflow(struct kvm_vcpu *vcpu, u64 select_idx)
> > {
> > - return (select_idx == ARMV8_PMU_CYCLE_IDX &&
> > - __vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_LC);
> > + u64 val = __vcpu_sys_reg(vcpu, PMCR_EL0);
> > +
> > + return (select_idx < ARMV8_PMU_CYCLE_IDX && (val & ARMV8_PMU_PMCR_LP)) ||
> > + (select_idx == ARMV8_PMU_CYCLE_IDX && (val & ARMV8_PMU_PMCR_LC));
> > }
> >
> > static bool kvm_pmu_counter_can_chain(struct kvm_vcpu *vcpu, u64 idx)
> > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > index c0595f31dab8..2b5e0ec5c100 100644
> > --- a/arch/arm64/kvm/sys_regs.c
> > +++ b/arch/arm64/kvm/sys_regs.c
> > @@ -654,6 +654,8 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> > | (ARMV8_PMU_PMCR_MASK & 0xdecafbad)) & (~ARMV8_PMU_PMCR_E);
> > if (!system_supports_32bit_el0())
> > val |= ARMV8_PMU_PMCR_LC;
> > + if (!kvm_pmu_is_3p5(vcpu))
> > + val &= ~ARMV8_PMU_PMCR_LP;
> > __vcpu_sys_reg(vcpu, r->reg) = val;
> > }
> >
> > @@ -703,6 +705,8 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> > val |= p->regval & ARMV8_PMU_PMCR_MASK;
> > if (!system_supports_32bit_el0())
> > val |= ARMV8_PMU_PMCR_LC;
> > + if (!kvm_pmu_is_3p5(vcpu))
> > + val &= ~ARMV8_PMU_PMCR_LP;
> > __vcpu_sys_reg(vcpu, PMCR_EL0) = val;
> > kvm_pmu_handle_pmcr(vcpu, val);
> > kvm_vcpu_pmu_restore_guest(vcpu);
> > diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> > index 6bda9b071084..846502251923 100644
> > --- a/include/kvm/arm_pmu.h
> > +++ b/include/kvm/arm_pmu.h
> > @@ -89,6 +89,13 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
> > vcpu->arch.pmu.events = *kvm_get_pmu_events(); \
> > } while (0)
> >
> > +/*
> > + * Evaluates as true when emulating PMUv3p5, and false otherwise.
> > + */
> > +#define kvm_pmu_is_3p5(vcpu) \
> > + (vcpu->kvm->arch.dfr0_pmuver >= ID_AA64DFR0_PMUVER_8_5 && \
> > + vcpu->kvm->arch.dfr0_pmuver != ID_AA64DFR0_PMUVER_IMP_DEF)
>
> I don't believe the IMP_DEF condition will ever evaluate to false as
> dfr0_pmuver is sanitized at initialization and writes from userspace.
Good point. That's a leftover from a previous version. I'll fix that.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
