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KVM: x86: hyper-v: Calculate APIC bus frequency for Hyper-V

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Remove APIC_BUS_FREQUENCY and calculate it based on nanoseconds per APIC
bus cycle.  APIC_BUS_FREQUENCY is used only for HV_X64_MSR_APIC_FREQUENCY.
The MSR is not frequently read, calculate it every time.

There are two constants related to the APIC bus frequency:
APIC_BUS_FREQUENCY and APIC_BUS_CYCLE_NS.
Only one value is required because one can be calculated from the other:
   APIC_BUS_CYCLES_NS = 1000 * 1000 * 1000 / APIC_BUS_FREQUENCY.

Remove APIC_BUS_FREQUENCY and instead calculate it when needed.
This prepares for support of configurable APIC bus frequency by
requiring to change only a single variable.

Suggested-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Maxim Levitsky <maximlevitsky@gmail.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
[reinette: rework changelog]
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/76a659d0898e87ebd73ee7c922f984a87a6ab370.1714081726.git.reinette.chatre@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Isaku Yamahata 2024-04-25 15:06:59 -07:00 committed by Sean Christopherson
parent 82897db912
commit f9e1cbf180
2 changed files with 1 additions and 2 deletions
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2
arch/x86/kvm/hyperv.c
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@ -1737,7 +1737,7 @@ 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);

1
arch/x86/kvm/lapic.h
View File

@ -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