On 12/19/2023 4:34 PM, Isaku Yamahata wrote:
+7.34 KVM_CAP_X86_BUS_FREQUENCY_CONTROL
+--------------------------------------
+
+:Architectures: x86
+:Target: VM
+:Parameters: args[0] is the value of apic bus clock frequency
+:Returns: 0 on success, -EINVAL if args[0] contains invalid value for the
+ frequency, or -ENXIO if virtual local APIC isn't enabled by
+ KVM_CREATE_IRQCHIP, or -EBUSY if any vcpu is created.
+
+This capability sets the APIC bus clock frequency (or core crystal clock
+frequency) for kvm to emulate APIC in the kernel.
Isaku,
you are mixing the `bus clock` and `core crystal clock` frequency. They
are different.
- When CPUID 0x15 doesn't exist, or CPUID 0x15 doesn't enumerate core
crystal clock frequency, the APIC timer frequency is the processor's bus
clock.
- When CPUID 0x15 does enumerate the core crystal clock frequency, the
APIC timer frequency is the core crystal clock frequency.
This patch only enables the user-configurable bus clock frequency, or
specifically APIC timer frequency. It doesn't enable the configuration
of core crystal clock frequency. Userspace can configure core crystal
clock frequency by passing a valid CPUID 0x15 leaf into KVM_SET_CPUID2,
not by this KVM_CAP.
The default value is 1000000
+(1GHz).
