Re: [PATCH v7 4/7] KVM: Add reset/restore rtc_status support

[Gleb Natapov <gleb@redhat.com>]

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@Intel.com>
> >>>> 
> >>>> Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
> >>>> ---
> >>>>  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.

--
			Gleb.