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

Paolo Bonzini
2016-12-14T15:50:45Z

On 14/12/2016 14:41, Radim Krčmář wrote:
> 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 ...

I can change it myself too.

Paolo