[PATCH v3 4/6] KVM: arm64: Use per guest ID register for ID_AA64DFR0_EL1.PMUVer
Reiji Watanabe
reijiw at google.com
Wed Mar 8 08:42:34 PST 2023
Hi Jing,
On Mon, Feb 27, 2023 at 10:23 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 | 52 ++++++++++++++++++++++++-------
> include/kvm/arm_pmu.h | 6 ++--
> 4 files changed, 51 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 6
>
> 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 36859e4caf02..21ec8fc10d79 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)
> @@ -256,10 +259,19 @@ 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);
> +
> + 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), pmuver);
The pmuver must be converted to perfmon for ID_DFR0_EL1.
Also, I think those registers should be updated atomically, although PMUver
specified by userspace will be normally the same for all vCPUs with
PMUv3 configured (I have the same comment for set_id_dfr0_el1()).
> + } 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;
> }
> @@ -296,10 +308,19 @@ 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));
The perfmon value should be set for ID_DFR0_EL1 (not pmuver).
> +
> + 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), 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;
> }
> @@ -543,4 +564,13 @@ 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) && \
What is the reason for adding this kvm_vcpu_has_pmu() checking ?
I don't think this patch's changes necessitated this.
> + 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);
>
> --
> 2.39.2.722.g9855ee24e9-goog
>
>
Thank you,
Reiji
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