Gleb Natapov wrote on 2013-04-07:
> On Sun, Apr 07, 2013 at 01:16:51PM +0000, Zhang, Yang Z wrote:
>> Gleb Natapov wrote on 2013-04-07:
>>> On Sun, Apr 07, 2013 at 01:05:02PM +0000, Zhang, Yang Z wrote:
>>>> Gleb Natapov wrote on 2013-04-07:
>>>>> On Sun, Apr 07, 2013 at 12:39:32PM +0000, Zhang, Yang Z wrote:
>>>>>> Gleb Natapov wrote on 2013-04-07:
>>>>>>> On Sun, Apr 07, 2013 at 02:30:15AM +0000, Zhang, Yang Z wrote:
>>>>>>>> Gleb Natapov wrote on 2013-04-04:
>>>>>>>>> On Mon, Apr 01, 2013 at 08:40:13AM +0800, Yang Zhang wrote:
>>>>>>>>>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>>>>>>>> ---
>>>>>>>>>> arch/x86/kvm/lapic.c | 9 +++++++++ arch/x86/kvm/lapic.h | 2
>>>>>>>>>> ++ virt/kvm/ioapic.c | 43
>>>>>>>>>> +++++++++++++++++++++++++++++++++++++++++++ virt/kvm/ioapic.h
>>>>>>>>>> | 1 + 4 files changed, 55 insertions(+), 0 deletions(-)
>>>>>>>>>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
>>>>>>>>>> index 96ab160..9c041fa 100644
>>>>>>>>>> --- a/arch/x86/kvm/lapic.c
>>>>>>>>>> +++ b/arch/x86/kvm/lapic.c
>>>>>>>>>> @@ -94,6 +94,14 @@ static inline int apic_test_vector(int vec, void
>>>>> *bitmap)
>>>>>>>>>> return test_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
>>>>>>>>>> }
>>>>>>>>>> +bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector)
>>>>>>>>>> +{
>>>>>>>>>> + struct kvm_lapic *apic = vcpu->arch.apic;
>>>>>>>>>> +
>>>>>>>>>> + return apic_test_vector(vector, apic->regs + APIC_ISR) ||
>>>>>>>>>> + apic_test_vector(vector, apic->regs + APIC_IRR);
>>>>>>>>>> +}
>>>>>>>>>> +
>>>>>>>>>> static inline void apic_set_vector(int vec, void *bitmap)
>>>>>>>>>> {
>>>>>>>>>> set_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
>>>>>>>>>> @@ -1665,6 +1673,7 @@ void kvm_apic_post_state_restore(struct
>>>>>>> kvm_vcpu
>>>>>>>>> *vcpu,
>>>>>>>>>> apic->highest_isr_cache = -1;
>>>>>>>>>> kvm_x86_ops->hwapic_isr_update(vcpu->kvm,
>>>>>>>>>> apic_find_highest_isr(apic)); kvm_make_request(KVM_REQ_EVENT,
>>>>>>>>>> vcpu); + kvm_rtc_irq_restore(vcpu); }
>>>>>>>>>>
>>>>>>>>>> void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
>>>>>>>>>> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
>>>>>>>>>> index 967519c..004d2ad 100644
>>>>>>>>>> --- a/arch/x86/kvm/lapic.h
>>>>>>>>>> +++ b/arch/x86/kvm/lapic.h
>>>>>>>>>> @@ -170,4 +170,6 @@ static inline bool
> kvm_apic_has_events(struct
>>>>>>>>> kvm_vcpu *vcpu)
>>>>>>>>>> return vcpu->arch.apic->pending_events;
>>>>>>>>>> }
>>>>>>>>>> +bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
>>>>>>>>>> +
>>>>>>>>>> #endif
>>>>>>>>>> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
>>>>>>>>>> index 8664812..0b12b17 100644
>>>>>>>>>> --- a/virt/kvm/ioapic.c
>>>>>>>>>> +++ b/virt/kvm/ioapic.c
>>>>>>>>>> @@ -90,6 +90,47 @@ static unsigned long
> ioapic_read_indirect(struct
>>>>>>>>> kvm_ioapic *ioapic,
>>>>>>>>>> return result;
>>>>>>>>>> }
>>>>>>>>>> +static void rtc_irq_reset(struct kvm_ioapic *ioapic)
>>>>>>>>>> +{
>>>>>>>>>> + ioapic->rtc_status.pending_eoi = 0;
>>>>>>>>>> + bitmap_zero(ioapic->rtc_status.dest_map, KVM_MAX_VCPUS);
>>>>>>>>>> +}
>>>>>>>>>> +
>>>>>>>>>> +static void rtc_irq_restore(struct kvm_ioapic *ioapic)
>>>>>>>>>> +{
>>>>>>>>>> + struct kvm_vcpu *vcpu;
>>>>>>>>>> + int vector, i, pending_eoi = 0;
>>>>>>>>>> +
>>>>>>>>>> + if (RTC_GSI >= IOAPIC_NUM_PINS)
>>>>>>>>>> + return;
>>>>>>>>>> +
>>>>>>>>>> + vector = ioapic->redirtbl[RTC_GSI].fields.vector;
>>>>>>>>>> + kvm_for_each_vcpu(i, vcpu, ioapic->kvm) {
>>>>>>>>>> + if (kvm_apic_pending_eoi(vcpu, vector)) {
>>>>>>>>>> + pending_eoi++;
>>>>>>>>>> + __set_bit(vcpu->vcpu_id,
>>> ioapic->rtc_status.dest_map);
>>>>>>>>> You should cleat dest_map at the beginning to get rid of stale bits.
>>>>>>>> I thought kvm_set_ioapic is called only after save/restore or migration.
>>> And
>>>>> the
>>>>>>> ioapic should be reset successfully before call it. So the
>>>>>>> dest_map is empty before call rtc_irq_restore().
>>>>>>>> But it is possible kvm_set_ioapic is called beside save/restore or
>>>>>>>> migration. Right?
>>>>>>>>
>>>>>>> First of all userspace should not care when it calls kvm_set_ioapic()
>>>>>>> the kernel need to do the right thing. Second, believe it or not,
>>>>>>> kvm_ioapic_reset() is not called during system reset. Instead userspace
>>>>>>> reset it by calling kvm_set_ioapic() with ioapic state after reset.
>>>>>> Ok. I see. As the logic you suggested, it will clear dest_map if no
>>>>>> pending eoi in vcpu, so we don't need to do it again.
>>>>>>
>>>>> You again rely on userspace doing thing in certain manner. What is
>>>>> set_lapic() is never called? Kernel internal state have to be correct
>>>>> after each ioctl call.
>>>> Sorry. I cannot figure out what's the problem if don't clear dest_map?
>>>> Can you elaborate it?
>>>>
>>> What is not obvious about it? If there is a bit in dest_map that should
>>> be cleared after rtc_irq_restore() it will not.
>> Why it will not? If new_val is false, and the old_val is true.
>> __clear_bit() will clear the dest_map. Am I wrong?
>>
> Ah, yes with new logic since we go over all vcpus and calculate new
> value for each one in theory it should be fine, but if we add cpu
> destruction this will be no longer true.
>
>> new_val = kvm_apic_pending_eoi(vcpu, vector);
> Which reminds me there are more bugs in the current code. It is not
> enough to call kvm_apic_pending_eoi() to check the new value. You need to
> see if the entry is masked and vcpu is the destination of the interrupt too.
No. kvm_apic_pending_eoi() is the right way. IOAPIC entry may change after vcpu received it before issue EOI, and we should not rely on the entry.
For example:
vcpu A received the interrupt, pending in IRR
mask entry
migration happened
The only problem is we may account the interrupt from non-IOAPIC(from IPI) into RTC interrupt. But it's ok, we will clear pending_eoi in EOI regardless of source.
Best regards,
Yang
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