Hi, Radim,
Got several questions inline.
On Fri, May 06, 2016 at 10:53:58PM +0200, Radim Krčmář wrote:
> x2APIC supports up to 2^32-1 LAPICs, but most guest in coming years will
> have slighly less VCPUs. Dynamic size saves memory at the cost of
> turning one constant into a variable.
>From the manual, I see x2apic only support 2^20-16 processors, not
2^32-1. Which one is correct?
>From below codes [1], I still see 2^20-16, since we are using high
16 bits of dest ID as cluster ID (0-0xfffe, while I guess 0xffff
should be reserved), and lower 16 bits as processor/lapic mask.
[...]
> +static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
> + u32 dest_id, struct kvm_lapic ***cluster, u16 *mask) {
> + switch (map->mode) {
> + case KVM_APIC_MODE_X2APIC: {
> + u32 offset = (dest_id >> 16) * 16;
> + // XXX: phys_map must be allocated as multiples of 16
> + if (offset < map->size) {
> + *cluster = &map->phys_map[offset];
> + *mask = dest_id & 0xffff;
[1]
[...]
> static void recalculate_apic_map(struct kvm *kvm)
> @@ -156,17 +162,28 @@ 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 size = 255;
>
> mutex_lock(&kvm->arch.apic_map_lock);
>
> + kvm_for_each_vcpu(i, vcpu, kvm)
> + if (kvm_apic_present(vcpu))
> + size = max(size, kvm_apic_id(vcpu->arch.apic));
> +
> + size++;
> + size += (16 - size) & 16;
Is this same as:
size = round_up(size, 16);
?
Thanks,
-- peterx
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