Re: [PATCH][v6] KVM: X86: support APERF/MPERF registers
From: Xiaoyao Li
Date: Fri Jun 05 2020 - 01:01:01 EST
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@xxxxxxxxx>
Signed-off-by: Chai Wen <chaiwen@xxxxxxxxx>
Signed-off-by: Jia Lina <jialina01@xxxxxxxxx>
---
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;