[RFC v2 2/9] KVM: ARM: VGIC: add forwarded irq rbtree lock

Eric Auger
2014-09-11T17:31:28Z

On 09/11/2014 05:09 AM, Christoffer Dall wrote:
> On Mon, Sep 01, 2014 at 02:52:41PM +0200, Eric Auger wrote:
>> add a lock related to the rb tree manipulation. The rb tree can be
>
> Ok, I can't hold myself back any longer.

Please begin sentences with a
> capital letter. You don't do this in French? :)
Hi Christoffer,

yep that's understood ;-) Definitively we do. Just that I am discovering
it is common too in commits and comments ;-)
>
>> searched in one thread (irqfd handler for instance) and map/unmap
>> happen in another.
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>> ---
>> include/kvm/arm_vgic.h | 1 +
>> virt/kvm/arm/vgic.c | 46 +++++++++++++++++++++++++++++++++++++---------
>> 2 files changed, 38 insertions(+), 9 deletions(-)
>>
>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>> index 743020f..3da244f 100644
>> --- a/include/kvm/arm_vgic.h
>> +++ b/include/kvm/arm_vgic.h
>> @@ -177,6 +177,7 @@ struct vgic_dist {
>> unsigned long irq_pending_on_cpu;
>>
>> struct rb_root irq_phys_map;
>> + spinlock_t rb_tree_lock;
>> #endif
>> };
>>
>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>> index 8ef495b..dbc2a5a 100644
>> --- a/virt/kvm/arm/vgic.c
>> +++ b/virt/kvm/arm/vgic.c
>> @@ -1630,9 +1630,15 @@ static struct rb_root *vgic_get_irq_phys_map(struct kvm_vcpu *vcpu,
>>
>> int vgic_map_phys_irq(struct kvm_vcpu *vcpu, int virt_irq, int phys_irq)
>> {
>> - struct rb_root *root = vgic_get_irq_phys_map(vcpu, virt_irq);
>> - struct rb_node **new = &root->rb_node, *parent = NULL;
>> + struct rb_root *root;
>> + struct rb_node **new, *parent = NULL;
>> struct irq_phys_map *new_map;
>> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>> +
>> + spin_lock(&dist->rb_tree_lock);
>> +
>> + root = vgic_get_irq_phys_map(vcpu, virt_irq);
>> + new = &root->rb_node;
>>
>> /* Boilerplate rb_tree code */
>> while (*new) {
>> @@ -1644,13 +1650,17 @@ int vgic_map_phys_irq(struct kvm_vcpu *vcpu, int virt_irq, int phys_irq)
>> new = &(*new)->rb_left;
>> else if (this->virt_irq > virt_irq)
>> new = &(*new)->rb_right;
>> - else
>> + else {
>> + spin_unlock(&dist->rb_tree_lock);
>> return -EEXIST;
>> + }
>
> can you initialize a ret variable to -EEXIST in the beginning of this
> function, and add an out label above the unlock below, replace this
> multi-line statement with a goto out, and set ret = 0 after the while
> loop?
sure
>
>> }
>>
>> new_map = kzalloc(sizeof(*new_map), GFP_KERNEL);
>> - if (!new_map)
>> + if (!new_map) {
>> + spin_unlock(&dist->rb_tree_lock);
>> return -ENOMEM;
>
> then this becomes ret = -ENOMEM; goto out;
OK
>
>> + }
>>
>> new_map->virt_irq = virt_irq;
>> new_map->phys_irq = phys_irq;
>> @@ -1658,6 +1668,8 @@ int vgic_map_phys_irq(struct kvm_vcpu *vcpu, int virt_irq, int phys_irq)
>> rb_link_node(&new_map->node, parent, new);
>> rb_insert_color(&new_map->node, root);
>>
>> + spin_unlock(&dist->rb_tree_lock);
>> +
>
> aren't you allocating memory with GFP_KERNEL while holding a spinlock
> here?
oups. Thanks for noticing. I Will move the lock.
>
>> return 0;
>> }
>>
>> @@ -1685,24 +1697,39 @@ static struct irq_phys_map *vgic_irq_map_search(struct kvm_vcpu *vcpu,
>>
>> int vgic_get_phys_irq(struct kvm_vcpu *vcpu, int virt_irq)
>> {
>> - struct irq_phys_map *map = vgic_irq_map_search(vcpu, virt_irq);
>> + struct irq_phys_map *map;
>> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>> + int ret;
>> +
>> + spin_lock(&dist->rb_tree_lock);
>> + map = vgic_irq_map_search(vcpu, virt_irq);
>>
>> if (map)
>> - return map->phys_irq;
>> + ret = map->phys_irq;
>> + else
>> + ret = -ENOENT;
>
> initialize ret to -ENOENT and avoid the else statement.
ok
>
>> +
>> + spin_unlock(&dist->rb_tree_lock);
>> + return ret;
>>
>> - return -ENOENT;
>> }
>>
>> int vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, int virt_irq, int phys_irq)
>> {
>> - struct irq_phys_map *map = vgic_irq_map_search(vcpu, virt_irq);
>> + struct irq_phys_map *map;
>> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>> +
>> + spin_lock(&dist->rb_tree_lock);
>> +
>> + map = vgic_irq_map_search(vcpu, virt_irq);
>>
>> if (map && map->phys_irq == phys_irq) {
>> rb_erase(&map->node, vgic_get_irq_phys_map(vcpu, virt_irq));
>> kfree(map);
>> + spin_unlock(&dist->rb_tree_lock);
>
> can kfree sleep? I don't remember. In any case, you can unlock before
> calling kfree.
no it can't but I will move anyway.
>
>> return 0;
>> }
>> -
>> + spin_unlock(&dist->rb_tree_lock);
>> return -ENOENT;
>
> an out label and single unlock location would be preferred here as well
> I think.
ok

Thansk

Eric
>
>> }
>>
>> @@ -1898,6 +1925,7 @@ int kvm_vgic_create(struct kvm *kvm)
>> }
>>
>> spin_lock_init(&kvm->arch.vgic.lock);
>> + spin_lock_init(&kvm->arch.vgic.rb_tree_lock);
>> kvm->arch.vgic.in_kernel = true;
>> kvm->arch.vgic.vctrl_base = vgic->vctrl_base;
>> kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF;
>> --
>> 1.9.1
>>