From: David Woodhouse <dwmw@xxxxxxxxxxxx> In https://lkml.org/lkml/2008/10/1/246 a proposal was made for generic CPUID leaves, of which only 0x40000010 was defined, to contain the TSC and local APIC frequencies. The proposal from VMware was mostly shot down in flames, *but* XNU does unconditionally assume that this leaf contains the frequency information, if it's present on any hypervisor: https://github.com/apple/darwin-xnu/blob/main/osfmk/i386/cpuid.c So does FreeBSD: https://github.com/freebsd/freebsd-src/commit/4a432614f68 So at this point it would be daft for a hypervisor to expose 0x40000010 for any *other* content. KVM might as well adopt it, and fill in the accurate TSC frequency just as it does for the Xen TSC leaf. Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> --- arch/x86/include/uapi/asm/kvm_para.h | 11 +++++++++++ arch/x86/kvm/cpuid.c | 7 +++++++ 2 files changed, 18 insertions(+) diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index a1efa7907a0b..1597c4a2a24a 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -44,6 +44,17 @@ */ #define KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24 + +/* + * Proposed by VMware in https://lkml.org/lkml/2008/10/1/246 the timing + * information leaf provides the TSC and local APIC timer frequencies: + * + * # EAX: (Virtual) TSC frequency in kHz. + * # EBX: (Virtual) Bus (local apic timer) frequency in kHz. + * # ECX, EDX: RESERVED (reserved fields are set to zero). + */ +#define KVM_CPUID_TIMING_INFO 0x40000010 + #define MSR_KVM_WALL_CLOCK 0x11 #define MSR_KVM_SYSTEM_TIME 0x12 diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index bcce3a75c3f2..1bd69d9c86b7 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -2029,6 +2029,13 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, } else if (index == 2) { *eax = vcpu->arch.hw_tsc_khz; } + } else if (vcpu->arch.kvm_cpuid.base && + function <= vcpu->arch.kvm_cpuid.limit && + function == (vcpu->arch.kvm_cpuid.base | KVM_CPUID_TIMING_INFO)) { + if (kvm_check_request(KVM_REQ_CLOCK_UPDATE, vcpu)) + kvm_guest_time_update(vcpu); + + *eax = vcpu->arch.hw_tsc_khz; } } else { *eax = *ebx = *ecx = *edx = 0; -- 2.49.0
