Re: [PATCH v2 2/4] KVM: x86: replace kvm_apic_id with kvm_{x,x2}apic_id

Radim Krčmář
2016-12-14T13:43:29Z

2016-12-14 13:39+0100, David Hildenbrand:
> Am 13.12.2016 um 17:29 schrieb Radim Krčmář:
>> There were three calls sites:
>> - recalculate_apic_map and kvm_apic_match_physical_addr, where it would
>> only complicate implementation of x2APIC hotplug;
>> - in apic_debug, where it was still somewhat preserved, but keeping the
>> old function just for apic_debug was not worth it
>>
>> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
>> ---
>> arch/x86/kvm/lapic.c | 41 ++++++++++++++++++++++++++++++-----------
>> arch/x86/kvm/lapic.h | 11 -----------
>> 2 files changed, 30 insertions(+), 22 deletions(-)
>>
>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
>> index 09edd32b8e42..e645b4bc6437 100644
>> --- a/arch/x86/kvm/lapic.c
>> +++ b/arch/x86/kvm/lapic.c
>> @@ -115,6 +115,16 @@ static inline int apic_enabled(struct kvm_lapic *apic)
>> (LVT_MASK | APIC_MODE_MASK | APIC_INPUT_POLARITY | \
>> APIC_LVT_REMOTE_IRR | APIC_LVT_LEVEL_TRIGGER)
>>
>> +static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
>> +{
>> + return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
>> +}
>> +
>> +static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
>> +{
>> + return apic->vcpu->vcpu_id;
>> +}
>> +
>> 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) {
>> @@ -159,13 +169,13 @@ static void recalculate_apic_map(struct kvm *kvm)
>> struct kvm_apic_map *new, *old = NULL;
>> struct kvm_vcpu *vcpu;
>> int i;
>> - u32 max_id = 255;
>> + u32 max_id = 256; /* enough space for any xAPIC ID */
>
> Why exactly do we have to increase this?
>
> I thought the maximum xapic id is 255, and we correctly allocate
> 255+1 slots.
>
> Now, we would allocate 257 slots and set max_apic_id to 256.

Right, it is a typical off-by-one error. The comment is sufficient ...

Queued for v3,
Thanks.