Re: [PATCH v3 6/9] KVM: arm/arm64: Introduce an allocator for in-kernel irq lines

Marc Zyngier
2017-06-08T15:05:26Z

On 08/06/17 15:59, Christoffer Dall wrote:
> On Thu, Jun 08, 2017 at 03:07:19PM +0100, Marc Zyngier wrote:
>> On Thu, Jun 08 2017 at 3:34:43 pm BST, Christoffer Dall <cdall@linaro.org> wrote:
>>> Having multiple devices being able to signal the same interrupt line is
>>> very confusing and almost certainly guarantees a configuration error.
>>>
>>> Therefore, introduce a very simple allocator which allows a device to
>>> claim an interrupt line from the vgic for a given VM.
>>>
>>> Signed-off-by: Christoffer Dall <cdall@linaro.org>
>>> ---
>>> include/kvm/arm_vgic.h | 5 +++++
>>> virt/kvm/arm/vgic/vgic.c | 33 +++++++++++++++++++++++++++++++++
>>> 2 files changed, 38 insertions(+)
>>>
>>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>>> index dde59fb..5d5b345 100644
>>> --- a/include/kvm/arm_vgic.h
>>> +++ b/include/kvm/arm_vgic.h
>>> @@ -121,6 +121,9 @@ struct vgic_irq {
>>> u8 source; /* GICv2 SGIs only */
>>> u8 priority;
>>> enum vgic_irq_config config; /* Level or edge */
>>> +
>>> + void *owner; /* Opaque pointer to reserve an interrupt
>>> + for in-kernel devices. */
>>> };
>>>
>>> struct vgic_register_region;
>>> @@ -340,4 +343,6 @@ int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi);
>>> */
>>> int kvm_vgic_setup_default_irq_routing(struct kvm *kvm);
>>>
>>> +int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner);
>>> +
>>> #endif /* __KVM_ARM_VGIC_H */
>>> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
>>> index c66feac..9628945 100644
>>> --- a/virt/kvm/arm/vgic/vgic.c
>>> +++ b/virt/kvm/arm/vgic/vgic.c
>>> @@ -435,6 +435,39 @@ int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int virt_irq)
>>> }
>>>
>>> /**
>>> + * kvm_vgic_set_owner - Set the owner of an interrupt for a VM
>>> + *
>>> + * @vcpu: Pointer to the VCPU (used for PPIs)
>>> + * @intid: The virtual INTID identifying the interrupt (PPI or SPI)
>>> + * @owner: Opaque pointer to the owner
>>> + *
>>> + * Returns 0 if intid is not already used by another in-kernel device and the
>>> + * owner is set, otherwise returns an error code.
>>> + */
>>> +int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
>>> +{
>>> + struct vgic_irq *irq;
>>> + int ret = 0;
>>> +
>>> + if (!vgic_initialized(vcpu->kvm))
>>> + return -EAGAIN;
>>> +
>>> + /* SGIs and LPIs cannot be wired up to any device */
>>> + if (!irq_is_ppi(intid) && !vgic_valid_spi(vcpu->kvm, intid))
>>> + return -EINVAL;
>>> +
>>> + irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
>>> + spin_lock(&irq->irq_lock);
>>> + if (irq->owner && irq->owner != owner)
>>> + ret = -EEXIST;
>>> + else
>>> + irq->owner = owner;
>>
>> Is there any case where you'd end-up setting the owner multiple times?
>> Or is that just convenient?
>>
>
> I think the timer code ended up doing that in some sequence, but maybe
> not. In any case, I'm not sure if it makes much of a difference?

None whatsoever.

Thanks,

M.
--
Jazz is not dead. It just smells funny...