Re: [PATCH 09/10] KVM: arm/arm64: vgic: Implement forwarding setting

Auger Eric
2017-05-30T14:03:15Z

Hi Marc,

On 30/05/2017 15:17, Marc Zyngier wrote:
> On 30/05/17 13:54, Auger Eric wrote:
>> Hi,
>>
>> On 25/05/2017 21:19, Marc Zyngier wrote:
>>> On Wed, May 24 2017 at 10:13:22 pm BST, Eric Auger <eric.auger@redhat.com> wrote:
>>>> Implements kvm_vgic_[set|unset]_forwarding.
>>>>
>>>> Handle low-level VGIC programming and consistent irqchip
>>>> programming.
>>>>
>>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>>>
>>>> ---
>>>> ---
>>>> include/kvm/arm_vgic.h | 5 +++
>>>> virt/kvm/arm/vgic/vgic.c | 105 +++++++++++++++++++++++++++++++++++++++++++++++
>>>> 2 files changed, 110 insertions(+)
>>>>
>>>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>>>> index 695ebc7..7ddac8a 100644
>>>> --- a/include/kvm/arm_vgic.h
>>>> +++ b/include/kvm/arm_vgic.h
>>>> @@ -343,4 +343,9 @@ 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_forwarding(struct kvm *kvm, unsigned int irq,
>>>> + unsigned int virt_irq);
>>>> +void kvm_vgic_unset_forwarding(struct kvm *kvm, unsigned int irq,
>>>> + unsigned int virt_irq);
>>>
>>> nit: the name of the variables do not match that of the function
>>> definition, and are much clearer there.
>>>
>>>> +
>>>> #endif /* __KVM_ARM_VGIC_H */
>>>> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
>>>> index aa0618c..c2add8d 100644
>>>> --- a/virt/kvm/arm/vgic/vgic.c
>>>> +++ b/virt/kvm/arm/vgic/vgic.c
>>>> @@ -17,6 +17,8 @@
>>>> #include <linux/kvm.h>
>>>> #include <linux/kvm_host.h>
>>>> #include <linux/list_sort.h>
>>>> +#include <linux/interrupt.h>
>>>> +#include <linux/irq.h>
>>>>
>>>> #include "vgic.h"
>>>>
>>>> @@ -771,3 +773,106 @@ bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int virt_irq)
>>>> return map_is_active;
>>>> }
>>>>
>>>> +/**
>>>> + * kvm_vgic_set_forwarding - Set IRQ forwarding
>>>> + *
>>>> + * @kvm: kvm handle
>>>> + * @host_irq: the host linux IRQ
>>>> + * @vintid: the virtual INTID
>>>> + *
>>>> + * This function must be called when the IRQ is not active:
>>>> + * ie. not active at GIC level and not currently under injection
>>>> + * into the guest using the unforwarded mode. The physical IRQ must
>>>> + * be disabled and all vCPUs must have been exited and prevented
>>>> + * from being re-entered.
>>>> + */
>>>> +int kvm_vgic_set_forwarding(struct kvm *kvm, unsigned int host_irq,
>>>> + unsigned int vintid)
>>>> +{
>>>> + struct kvm_vcpu *vcpu;
>>>> + struct vgic_irq *irq;
>>>> + struct irq_desc *desc;
>>>> + struct irq_data *data;
>>>> + unsigned int pintid;
>>>> + int ret = 0;
>>>> +
>>>> +
>>>> + kvm_debug("%s host linux irq=%d vintid=%d\n",
>>>> + __func__, host_irq, vintid);
>>>> +
>>>> + if (!vgic_valid_spi(kvm, vintid))
>>>> + return 0;
>>>> +
>>>> + /* find the INTID corresponding to @host_irq */
>>>> + desc = irq_to_desc(host_irq);
>>>> + if (!desc) {
>>>> + kvm_err("%s: no interrupt descriptor\n", __func__);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + data = irq_desc_get_irq_data(desc);
>>>> + while (data->parent_data)
>>>> + data = data->parent_data;
>>>> +
>>>> + pintid = data->hwirq;
>>>> +
>>>> + irq = vgic_get_irq(kvm, NULL, vintid);
>>>> +
>>>> + spin_lock(&irq->irq_lock);
>>>> +
>>>> + vcpu = irq->target_vcpu;
>>>> +
>>>> + if (!vcpu) {
>>>> + ret = -EAGAIN;
>>>> + goto unlock;
>>>> + }
>>>> +
>>>> + irq_set_vcpu_affinity(host_irq, vcpu);
>>>> +
>>>> + irq->hw = true;
>>>> + irq->hwintid = pintid;
>>>> + irq->host_irq = host_irq;
>>>
>>> This feels like a duplication of kvm_vgic_map_phys_irq(), specially if
>>> you move the pintid discovery there. Can we somehow unify them?
>> Sure. At the beginning it was just a matter of irq_lock I did not want
>> to release.
>>
>> I was somehow embarrassed by the vcpu param of irq_set_vcpu_affinity.
>> Shall we really test target_vcpu. The actual value is unused for SPI so
>> shouldn't we simply use something != NULL.
>
> I guess that for the time being, this would be good enough. But GICv4
> requires some actual tracking of the affinity, so we may have to bite
> the bullet already, and decide that the interrupt is always affine to a
> vcpu.
>
> Does this have any userspace visible impact?
I don't see any.

Thanks

Eric
>
> Thanks,
>
> M.
>