Re: [PATCH v3 04/14] KVM: x86: dynamic kvm_apic_map

Radim Krčmář
2016-08-02T12:22:45Z

2016-08-02 19:39+0800, Wanpeng Li:
> 2016-07-13 4:09 GMT+08:00 Radim Krčmář <rkrcmar@redhat.com>:
> [...]
>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
>> @@ -152,14 +152,22 @@ static void recalculate_apic_map(struct kvm *kvm)
>> struct kvm_apic_map *new, *old = NULL;
>> struct kvm_vcpu *vcpu;
>> int i;
>> -
>> - new = kzalloc(sizeof(struct kvm_apic_map), GFP_KERNEL);
>> + u32 max_id = 255;
>
> If this should be max_id = KVM_MAX_VCPU_ID? I have a patch on hand to
> fix it, but I didn't know whether it is your desired behavior or not.

No, we could just have static array then. KVM_MAX_VCPU_ID is expected
to be raised to INT_MAX and eventually UINT_MAX, so it would not be
practical. The dynamic array is there to avoid wasting space in the
common case, where VMs have only low APIC IDs.

Inintial patches had 255 to minimize a chance of regressions as the
static array was that big, but starting with max_id = 0 is our goal and
should be ok even without other changes.