Re: [RFC 16/17] KVM: eventfd: add irq bypass consumer management

Eric Auger
2015-07-06T11:20:16Z

Hi Feng,
On 07/06/2015 09:55 AM, Wu, Feng wrote:
>
>
>> -----Original Message-----
>> From: Eric Auger [mailto:eric.auger@linaro.org]
>> Sent: Thursday, July 02, 2015 9:17 PM
>> To: eric.auger@st.com; eric.auger@linaro.org;
>> linux-arm-kernel@lists.infradead.org; kvmarm@lists.cs.columbia.edu;
>> kvm@vger.kernel.org; christoffer.dall@linaro.org; marc.zyngier@arm.com;
>> alex.williamson@redhat.com; pbonzini@redhat.com; avi.kivity@gmail.com;
>> mtosatti@redhat.com; Wu, Feng; joro@8bytes.org;
>> b.reynal@virtualopensystems.com
>> Cc: linux-kernel@vger.kernel.org; patches@linaro.org
>> Subject: [RFC 16/17] KVM: eventfd: add irq bypass consumer management
>>
>> This patch adds the registration/unregistration of an
>> irq_bypass_consumer on irqfd assignment/deassignment.
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>> ---
>> virt/kvm/eventfd.c | 22 +++++++++++++++++++---
>> 1 file changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
>> index f3da161..425a47b 100644
>> --- a/virt/kvm/eventfd.c
>> +++ b/virt/kvm/eventfd.c
>> @@ -34,6 +34,7 @@
>> #include <linux/srcu.h>
>> #include <linux/slab.h>
>> #include <linux/seqlock.h>
>> +#include <linux/irqbypass.h>
>> #include <trace/events/kvm.h>
>>
>> #include <kvm/iodev.h>
>> @@ -93,6 +94,7 @@ struct _irqfd {
>> struct list_head list;
>> poll_table pt;
>> struct work_struct shutdown;
>> + struct irq_bypass_consumer *cons;
>> };
>>
>> static struct workqueue_struct *irqfd_cleanup_wq;
>> @@ -429,7 +431,21 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd
>> *args)
>> */
>> fdput(f);
>>
>> - /* irq_bypass_register_consumer(); */
>> + irqfd->cons = kzalloc(sizeof(struct irq_bypass_consumer),
>> + GFP_KERNEL);
>> + if (!irqfd->cons) {
>> + ret = -ENOMEM;
>> + goto fail;
>> + }
>> + irqfd->cons->token = (void *)irqfd->eventfd;
>> + irqfd->cons->gsi = irqfd->gsi;
>> + irqfd->cons->kvm = kvm;
>> + irqfd->cons->add_producer = kvm_arch_add_producer;
>> + irqfd->cons->del_producer = kvm_arch_del_producer;
>> + irqfd->cons->stop_consumer = kvm_arch_stop_consumer;
>> + irqfd->cons->resume_consumer = kvm_arch_resume_consumer;
>> + ret = irq_bypass_register_consumer(irqfd->cons);
>> + WARN_ON(ret);
>>
>> return 0;
>>
>> @@ -530,8 +546,6 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd
>> *args)
>> struct _irqfd *irqfd, *tmp;
>> struct eventfd_ctx *eventfd;
>>
>> - /* irq_bypass_unregister_consumer() */
>> -
>> eventfd = eventfd_ctx_fdget(args->fd);
>> if (IS_ERR(eventfd))
>> return PTR_ERR(eventfd);
>> @@ -550,6 +564,8 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd
>> *args)
>> irqfd->irq_entry.type = 0;
>> write_seqcount_end(&irqfd->irq_entry_sc);
>> irqfd_deactivate(irqfd);
>> + irq_bypass_unregister_consumer(irqfd->cons);
>> + kfree(irqfd->cons);
>
> There may be an issue here. 'irqfd' is freed in irqfd_deactivate() --> ... --.>irqfd_shutdown(),
> and irqfd_deactivate() can be called in the other two places below:
> - irqfd_wakeup()
> - kvm_irqfd_release()
> I think we also need to call irq_bypass_unregister_consumer() there, right?
yes you're right. what about doing the unregistration in irqfd_shutdown
then?

Thanks for spotting this.

Eric

>
> Thanks,
> Feng
>
>
>> }
>> }
>>
>> --
>> 1.9.1
>