[PATCH v2 4/6] KVM: arm64: Use per guest ID register for ID_AA64DFR0_EL1.PMUVer
Reiji Watanabe
reijiw at google.com
Fri Feb 24 18:35:47 PST 2023
Hi Jing,
On Sun, Feb 12, 2023 at 1:58 PM Jing Zhang <jingzhangos at google.com> wrote:
>
> With per guest ID registers, PMUver settings from userspace
> can be stored in its corresponding ID register.
>
> No functional change intended.
>
> Signed-off-by: Jing Zhang <jingzhangos at google.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 11 ++++----
> arch/arm64/kvm/arm.c | 6 -----
> arch/arm64/kvm/id_regs.c | 44 +++++++++++++++++++++++--------
> include/kvm/arm_pmu.h | 6 +++--
> 4 files changed, 43 insertions(+), 24 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index f64347eb77c2..effb61a9a855 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -218,6 +218,12 @@ struct kvm_arch {
> #define KVM_ARCH_FLAG_EL1_32BIT 4
> /* PSCI SYSTEM_SUSPEND enabled for the guest */
> #define KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED 5
> + /*
> + * AA64DFR0_EL1.PMUver was set as ID_AA64DFR0_EL1_PMUVer_IMP_DEF
> + * or DFR0_EL1.PerfMon was set as ID_DFR0_EL1_PerfMon_IMPDEF from
> + * userspace for VCPUs without PMU.
> + */
> +#define KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU
As Oliver suggested, it might be better to not expose IMPDEF PMU
(but expose as 0), since it is not effectively supported by KVM.
(We need to be careful not to have migration from old KVM fail though)
>
> unsigned long flags;
>
> @@ -230,11 +236,6 @@ struct kvm_arch {
>
> cpumask_var_t supported_cpus;
>
> - struct {
> - u8 imp:4;
> - u8 unimp:4;
> - } dfr0_pmuver;
> -
> /* Hypercall features firmware registers' descriptor */
> struct kvm_smccc_features smccc_feat;
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index c78d68d011cb..fb2de2cb98cb 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -138,12 +138,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> kvm_arm_set_default_id_regs(kvm);
> kvm_arm_init_hypercalls(kvm);
>
> - /*
> - * Initialise the default PMUver before there is a chance to
> - * create an actual PMU.
> - */
> - kvm->arch.dfr0_pmuver.imp = kvm_arm_pmu_get_pmuver_limit();
> -
> return 0;
>
> err_free_cpumask:
> diff --git a/arch/arm64/kvm/id_regs.c b/arch/arm64/kvm/id_regs.c
> index bc4c408a43eb..14ae03a1d8d0 100644
> --- a/arch/arm64/kvm/id_regs.c
> +++ b/arch/arm64/kvm/id_regs.c
> @@ -21,9 +21,12 @@
> static u8 vcpu_pmuver(const struct kvm_vcpu *vcpu)
> {
> if (kvm_vcpu_has_pmu(vcpu))
> - return vcpu->kvm->arch.dfr0_pmuver.imp;
> -
> - return vcpu->kvm->arch.dfr0_pmuver.unimp;
> + return FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer),
> + IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1));
> + else if (test_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags))
> + return ID_AA64DFR0_EL1_PMUVer_IMP_DEF;
> + else
> + return 0;
> }
>
> static u8 perfmon_to_pmuver(u8 perfmon)
> @@ -267,10 +270,15 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
> if (val)
> return -EINVAL;
>
> - if (valid_pmu)
> - vcpu->kvm->arch.dfr0_pmuver.imp = pmuver;
> - else
> - vcpu->kvm->arch.dfr0_pmuver.unimp = pmuver;
> + if (valid_pmu) {
> + IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer);
> + IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1) |=
> + FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), pmuver);
The original code keeps ID_AA64DFR0_EL1.PMUVer and ID_DFR0_EL1.PerfMon
values consistent (if one of them is update, the other one is also
updated accordingly). To keep the same behavior, shouldn't we update
the other one as well when one of them is updated ?
Thank you,
Reiji
> + } else if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF) {
> + set_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
> + } else {
> + clear_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
> + }
>
> return 0;
> }
> @@ -307,10 +315,15 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
> if (val)
> return -EINVAL;
>
> - if (valid_pmu)
> - vcpu->kvm->arch.dfr0_pmuver.imp = perfmon_to_pmuver(perfmon);
> - else
> - vcpu->kvm->arch.dfr0_pmuver.unimp = perfmon_to_pmuver(perfmon);
> + if (valid_pmu) {
> + IDREG(vcpu->kvm, SYS_ID_DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_DFR0_EL1_PerfMon);
> + IDREG(vcpu->kvm, SYS_ID_DFR0_EL1) |=
> + FIELD_PREP(ARM64_FEATURE_MASK(ID_DFR0_EL1_PerfMon), perfmon_to_pmuver(perfmon));
> + } else if (perfmon == ID_DFR0_EL1_PerfMon_IMPDEF) {
> + set_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
> + } else {
> + clear_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
> + }
>
> return 0;
> }
> @@ -534,4 +547,13 @@ void kvm_arm_set_default_id_regs(struct kvm *kvm)
> }
>
> IDREG(kvm, SYS_ID_AA64PFR0_EL1) = val;
> +
> + /*
> + * Initialise the default PMUver before there is a chance to
> + * create an actual PMU.
> + */
> + IDREG(kvm, SYS_ID_AA64DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer);
> + IDREG(kvm, SYS_ID_AA64DFR0_EL1) |=
> + FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer),
> + kvm_arm_pmu_get_pmuver_limit());
> }
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 628775334d5e..eef67b7d9751 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -92,8 +92,10 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
> /*
> * Evaluates as true when emulating PMUv3p5, and false otherwise.
> */
> -#define kvm_pmu_is_3p5(vcpu) \
> - (vcpu->kvm->arch.dfr0_pmuver.imp >= ID_AA64DFR0_EL1_PMUVer_V3P5)
> +#define kvm_pmu_is_3p5(vcpu) \
> + (kvm_vcpu_has_pmu(vcpu) && \
> + FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), \
> + IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1)) >= ID_AA64DFR0_EL1_PMUVer_V3P5)
>
> u8 kvm_arm_pmu_get_pmuver_limit(void);
>
> --
> 2.39.1.581.gbfd45094c4-goog
>
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