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

Wu, Feng
2015-07-06T07:55:47Z

> -----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?

Thanks,
Feng

> }
> }
>
> --
> 1.9.1