RE: [PATCH v8 03/13] KVM: Define a new interface kvm_intr_is_single_vcpu()

["Wu, Feng" <feng.wu@intel.com>]

> -----Original Message-----
> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> Sent: Wednesday, September 16, 2015 5:23 PM
> To: Wu, Feng; alex.williamson@redhat.com; joro@8bytes.org;
> mtosatti@redhat.com
> Cc: eric.auger@linaro.org; kvm@vger.kernel.org;
> iommu@lists.linux-foundation.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v8 03/13] KVM: Define a new interface
> kvm_intr_is_single_vcpu()
> 
> 
> 
> On 16/09/2015 10:49, Feng Wu wrote:
> > This patch defines a new interface kvm_intr_is_single_vcpu(),
> > which can returns whether the interrupt is for single-CPU or not.
> >
> > It is used by VT-d PI, since now we only support single-CPU
> > interrupts, For lowest-priority interrupts, if user configures
> > it via /proc/irq or uses irqbalance to make it single-CPU, we
> > can use PI to deliver the interrupts to it. Full functionality
> > of lowest-priority support will be added later.
> >
> > Signed-off-by: Feng Wu <feng.wu@intel.com>
> > ---
> > v8:
> > - Some optimizations in kvm_intr_is_single_vcpu().
> > - Expose kvm_intr_is_single_vcpu() so we can use it in vmx code.
> > - Add kvm_intr_is_single_vcpu_fast() as the fast path to find
> >   the target vCPU for the single-destination interrupt
> >
> >  arch/x86/include/asm/kvm_host.h |  3 ++
> >  arch/x86/kvm/irq_comm.c         | 94
> +++++++++++++++++++++++++++++++++++++++++
> >  arch/x86/kvm/lapic.c            |  5 +--
> >  arch/x86/kvm/lapic.h            |  2 +
> >  4 files changed, 101 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> > index 49ec903..af11bca 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1204,4 +1204,7 @@ int __x86_set_memory_region(struct kvm *kvm,
> >  int x86_set_memory_region(struct kvm *kvm,
> >  			  const struct kvm_userspace_memory_region *mem);
> >
> > +bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
> > +			     struct kvm_vcpu **dest_vcpu);
> > +
> >  #endif /* _ASM_X86_KVM_HOST_H */
> > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> > index 9efff9e..97ba1d6 100644
> > --- a/arch/x86/kvm/irq_comm.c
> > +++ b/arch/x86/kvm/irq_comm.c
> > @@ -297,6 +297,100 @@ out:
> >  	return r;
> >  }
> >
> > +static bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm,
> > +					 struct kvm_lapic_irq *irq,
> > +					 struct kvm_vcpu **dest_vcpu)
> 
> Please put this in lapic.c, similar to kvm_irq_delivery_to_apic_fast, so
> that you do not have to export other functions.
> 
> > +{
> > +	struct kvm_apic_map *map;
> > +	bool ret = false;
> > +	struct kvm_lapic *dst = NULL;
> > +
> > +	if (irq->shorthand)
> > +		return false;
> > +
> > +	rcu_read_lock();
> > +	map = rcu_dereference(kvm->arch.apic_map);
> > +
> > +	if (!map)
> > +		goto out;
> > +
> > +	if (irq->dest_mode == APIC_DEST_PHYSICAL) {
> > +		if (irq->dest_id == 0xFF)
> > +			goto out;
> > +
> > +		if (irq->dest_id >= ARRAY_SIZE(map->phys_map)) {
> 
> Warning here is wrong, the guest can trigger it.

Could you please share more information about how the guest
triggers these conditions (including the following two), Thanks
a lot!

Thanks,
Feng

> 
> > +			WARN_ON_ONCE(1);
> > +			goto out;
> > +		}
> > +
> > +		dst = map->phys_map[irq->dest_id];
> > +		if (dst && kvm_apic_present(dst->vcpu))
> > +			*dest_vcpu = dst->vcpu;
> > +		else
> > +			goto out;
> > +	} else {
> > +		u16 cid;
> > +		unsigned long bitmap = 1;
> > +		int i, r = 0;
> > +
> > +		if (!kvm_apic_logical_map_valid(map)) {
> > +			WARN_ON_ONCE(1);
> 
> Same here.
> 
> > +			goto out;
> > +		}
> > +
> > +		apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap);
> > +
> > +		if (cid >= ARRAY_SIZE(map->logical_map)) {
> > +			WARN_ON_ONCE(1);
> 
> Same here.
> 
> Otherwise looks good.
> 
> Paolo
> 
> > +			goto out;
> > +		}
> > +
> > +		for_each_set_bit(i, &bitmap, 16) {
> > +			dst = map->logical_map[cid][i];
> > +			if (++r == 2)
> > +				goto out;
> > +		}
> > +
> > +		if (dst && kvm_apic_present(dst->vcpu))
> > +			*dest_vcpu = dst->vcpu;
> > +		else
> > +			goto out;
> > +	}
> > +
> > +	ret = true;
> > +out:
> > +	rcu_read_unlock();
> > +	return ret;
> > +}
> > +
> > +
> > +bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
> > +			     struct kvm_vcpu **dest_vcpu)
> > +{
> > +	int i, r = 0;
> > +	struct kvm_vcpu *vcpu;
> > +
> > +	if (kvm_intr_is_single_vcpu_fast(kvm, irq, dest_vcpu))
> > +		return true;
> > +
> > +	kvm_for_each_vcpu(i, vcpu, kvm) {
> > +		if (!kvm_apic_present(vcpu))
> > +			continue;
> > +
> > +		if (!kvm_apic_match_dest(vcpu, NULL, irq->shorthand,
> > +					irq->dest_id, irq->dest_mode))
> > +			continue;
> > +
> > +		if (++r == 2)
> > +			return false;
> > +
> > +		*dest_vcpu = vcpu;
> > +	}
> > +
> > +	return r == 1;
> > +}
> > +EXPORT_SYMBOL_GPL(kvm_intr_is_single_vcpu);
> > +
> >  #define IOAPIC_ROUTING_ENTRY(irq) \
> >  	{ .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,	\
> >  	  .u.irqchip = { .irqchip = KVM_IRQCHIP_IOAPIC, .pin = (irq) } }
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index 2a5ca97..9848cd50 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -136,13 +136,12 @@ static inline int kvm_apic_id(struct kvm_lapic
> *apic)
> >  /* The logical map is definitely wrong if we have multiple
> >   * modes at the same time.  (Physical map is always right.)
> >   */
> > -static inline bool kvm_apic_logical_map_valid(struct kvm_apic_map *map)
> > +bool kvm_apic_logical_map_valid(struct kvm_apic_map *map)
> >  {
> >  	return !(map->mode & (map->mode - 1));
> >  }
> >
> > -static inline void
> > -apic_logical_id(struct kvm_apic_map *map, u32 dest_id, u16 *cid, u16 *lid)
> > +void apic_logical_id(struct kvm_apic_map *map, u32 dest_id, u16 *cid, u16
> *lid)
> >  {
> >  	unsigned lid_bits;
> >
> > diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> > index 7195274..6798b87 100644
> > --- a/arch/x86/kvm/lapic.h
> > +++ b/arch/x86/kvm/lapic.h
> > @@ -169,4 +169,6 @@ bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu,
> int vector);
> >
> >  void wait_lapic_expire(struct kvm_vcpu *vcpu);
> >
> > +void apic_logical_id(struct kvm_apic_map *map, u32 dest_id, u16 *cid, u16
> *lid);
> > +bool kvm_apic_logical_map_valid(struct kvm_apic_map *map);
> >  #endif
> >