Messages in this thread Patch in this message | | | Subject | Re: [PATCH][v6] KVM: X86: support APERF/MPERF registers | From | Xiaoyao Li <> | Date | Fri, 5 Jun 2020 13:00:53 +0800 |
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On 6/5/2020 9:44 AM, Li RongQing wrote: > Guest kernel reports a fixed cpu frequency in /proc/cpuinfo, > this is confused to user when turbo is enable, and aperf/mperf > can be used to show current cpu frequency after 7d5905dc14a > "(x86 / CPU: Always show current CPU frequency in /proc/cpuinfo)" > so guest should support aperf/mperf capability > > This patch implements aperf/mperf by three mode: none, software > emulation, and pass-through > > None: default mode, guest does not support aperf/mperf > > Software emulation: the period of aperf/mperf in guest mode are > accumulated as emulated value > > Pass-though: it is only suitable for KVM_HINTS_REALTIME, Because > that hint guarantees we have a 1:1 vCPU:CPU binding and guaranteed > no over-commit. > > And a per-VM capability is added to configure aperfmperf mode > > Signed-off-by: Li RongQing <lirongqing@baidu.com> > Signed-off-by: Chai Wen <chaiwen@baidu.com> > Signed-off-by: Jia Lina <jialina01@baidu.com> > --- > diff v5: > return error if guest is configured with mperf/aperf, but host cpu has not > > diff v4: > fix maybe-uninitialized warning > > diff v3: > fix interception of MSR_IA32_MPERF/APERF in svm > > diff v2: > support aperfmperf pass though > move common codes to kvm_get_msr_common > > diff v1: > 1. support AMD, but not test > 2. support per-vm capability to enable > > > Documentation/virt/kvm/api.rst | 10 ++++++++++ > arch/x86/include/asm/kvm_host.h | 11 +++++++++++ > arch/x86/kvm/cpuid.c | 15 ++++++++++++++- > arch/x86/kvm/svm/svm.c | 8 ++++++++ > arch/x86/kvm/vmx/vmx.c | 6 ++++++ > arch/x86/kvm/x86.c | 42 +++++++++++++++++++++++++++++++++++++++++ > arch/x86/kvm/x86.h | 15 +++++++++++++++ > include/uapi/linux/kvm.h | 1 + > 8 files changed, 107 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index d871dacb984e..f854f4da6fd8 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6126,3 +6126,13 @@ KVM can therefore start protected VMs. > This capability governs the KVM_S390_PV_COMMAND ioctl and the > KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected > guests when the state change is invalid. > + > +8.23 KVM_CAP_APERFMPERF > +---------------------------- > + > +:Architectures: x86 > +:Parameters: args[0] is aperfmperf mode; > + 0 for not support, 1 for software emulation, 2 for pass-through > +:Returns: 0 on success; -1 on error > + > +This capability indicates that KVM supports APERF and MPERF MSR registers > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index fd78bd44b2d6..14643f8af9c4 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -824,6 +824,9 @@ struct kvm_vcpu_arch { > > /* AMD MSRC001_0015 Hardware Configuration */ > u64 msr_hwcr; > + > + u64 v_mperf; > + u64 v_aperf; > }; > > struct kvm_lpage_info { > @@ -889,6 +892,12 @@ enum kvm_irqchip_mode { > KVM_IRQCHIP_SPLIT, /* created with KVM_CAP_SPLIT_IRQCHIP */ > }; > > +enum kvm_aperfmperf_mode { > + KVM_APERFMPERF_NONE, > + KVM_APERFMPERF_SOFT, /* software emulate aperfmperf */ > + KVM_APERFMPERF_PT, /* pass-through aperfmperf to guest */ > +}; > + > #define APICV_INHIBIT_REASON_DISABLE 0 > #define APICV_INHIBIT_REASON_HYPERV 1 > #define APICV_INHIBIT_REASON_NESTED 2 > @@ -986,6 +995,8 @@ struct kvm_arch { > > struct kvm_pmu_event_filter *pmu_event_filter; > struct task_struct *nx_lpage_recovery_thread; > + > + enum kvm_aperfmperf_mode aperfmperf_mode; > }; > > struct kvm_vm_stat { > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index cd708b0b460a..80f18b29a845 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -122,6 +122,16 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > MSR_IA32_MISC_ENABLE_MWAIT); > } > > + best = kvm_find_cpuid_entry(vcpu, 6, 0); > + if (best) { > + if (guest_has_aperfmperf(vcpu->kvm)) { > + if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) > + return -EINVAL;
kvm_vm_ioctl_enable_cap() ensures that guest_has_aperfmperf() always aligns with boot_cpu_has(X86_FEATURE_APERFMPERF). So above is unnecessary.
> + best->ecx |= 1; > + } else { > + best->ecx &= ~1; > + } > + }
you could do
bool guest_cpuid_aperfmperf = false; if (best) guest_cpuid_aperfmperf = !!(best->ecx & BIT(0));
if (guest_cpuid_aperfmerf != guest_has_aperfmperf(vcpu->kvm)) return -EINVAL;
In fact, I think we can do nothing here. Leave it as what usersapce wants just like how KVM treats other CPUID bits.
Paolo,
What's your point?
> /* Note, maxphyaddr must be updated before tdp_level. */ > vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); > vcpu->arch.tdp_level = kvm_x86_ops.get_tdp_level(vcpu);
[...]
> @@ -4930,6 +4939,11 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > kvm->arch.exception_payload_enabled = cap->args[0]; > r = 0; > break; > + case KVM_CAP_APERFMPERF: > + kvm->arch.aperfmperf_mode = > + boot_cpu_has(X86_FEATURE_APERFMPERF) ? cap->args[0] : 0;
Shouldn't check whether cap->args[0] is a valid value?
> + r = 0; > + break; > default: > r = -EINVAL; > break;
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