Re: [PATCH v3 1/4] KVM: x86/hyperv: Calculate APIC bus frequency for hyper-v

[Xiaoyao Li]

On 12/21/2023 1:26 PM, Xiaoyao Li wrote:
> On 12/19/2023 4:34 PM, Isaku Yamahata wrote:
> > Remove APIC_BUS_FREUQNCY and calculate it based on APIC bus cycles per 
> > NS.
> > APIC_BUS_FREUQNCY is used only for HV_X64_MSR_APIC_FREQUENCY.  The MSR is
> > not frequently read, calculate it every time.
> >
> > In order to make APIC bus frequency configurable, we need to make make 
> > two
>
> two 'make', please drop one.

With this and other typos pointed by Maxim fixed.

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>

> > related constants into variables.  APIC_BUS_FREUQNCY and 
> > APIC_BUS_CYCLE_NS.
> > One can be calculated from the other.
> >     APIC_BUS_CYCLES_NS = 1000 * 1000 * 1000 / APIC_BUS_FREQUENCY.
> > By removing APIC_BUS_FREQUENCY, we need to track only single variable
> > instead of two.
> >
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > ---
> > Changes v3:
> > - Newly added according to Maxim Levistsky suggestion.
> > ---
> >   arch/x86/kvm/hyperv.c | 2 +-
> >   arch/x86/kvm/lapic.h  | 1 -
> >   2 files changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> > index 238afd7335e4..a40ca2fef58c 100644
> > --- a/arch/x86/kvm/hyperv.c
> > +++ b/arch/x86/kvm/hyperv.c
> > @@ -1687,7 +1687,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, 
> > u32 msr, u64 *pdata,
> >           data = (u64)vcpu->arch.virtual_tsc_khz * 1000;
> >           break;
> >       case HV_X64_MSR_APIC_FREQUENCY:
> > -        data = APIC_BUS_FREQUENCY;
> > +        data = div64_u64(1000000000ULL, APIC_BUS_CYCLE_NS);
> >           break;
> >       default:
> >           kvm_pr_unimpl_rdmsr(vcpu, msr);
> > diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> > index 0a0ea4b5dd8c..a20cb006b6c8 100644
> > --- a/arch/x86/kvm/lapic.h
> > +++ b/arch/x86/kvm/lapic.h
> > @@ -17,7 +17,6 @@
> >   #define APIC_DEST_MASK            0x800
> >   #define APIC_BUS_CYCLE_NS       1
> > -#define APIC_BUS_FREQUENCY      (1000000000ULL / APIC_BUS_CYCLE_NS)
> >   #define APIC_BROADCAST            0xFF
> >   #define X2APIC_BROADCAST        0xFFFFFFFFul