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

Wu, Feng
2015-07-06T12:18:15Z

> -----Original Message-----
> From: Eric Auger [mailto:eric.auger@linaro.org]
> Sent: Monday, July 06, 2015 7:20 PM
> To: Wu, Feng; eric.auger@st.com; 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; joro@8bytes.org; b.reynal@virtualopensystems.com
> Cc: linux-kernel@vger.kernel.org; patches@linaro.org
> Subject: Re: [RFC 16/17] KVM: eventfd: add irq bypass consumer management
>
> 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?

I am fine with this!

Thanks,
Feng
>
> Thanks for spotting this.
>
> Eric
>
> >
> > Thanks,
> > Feng
> >
> >
> >> }
> >> }
> >>
> >> --
> >> 1.9.1
> >