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

[Wu, Feng]

> -----Original Message-----
> From: Eric Auger [mailto:eric.auger@xxxxxxxxxx]
> Sent: Monday, July 06, 2015 7:20 PM
> To: Wu, Feng; eric.auger@xxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> kvmarm@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx;
> christoffer.dall@xxxxxxxxxx; marc.zyngier@xxxxxxx;
> alex.williamson@xxxxxxxxxx; pbonzini@xxxxxxxxxx; avi.kivity@xxxxxxxxx;
> mtosatti@xxxxxxxxxx; joro@xxxxxxxxxx; b.reynal@xxxxxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; patches@xxxxxxxxxx
> 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@xxxxxxxxxx]
> >> Sent: Thursday, July 02, 2015 9:17 PM
> >> To: eric.auger@xxxxxx; eric.auger@xxxxxxxxxx;
> >> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; kvmarm@xxxxxxxxxxxxxxxxxxxxx;
> >> kvm@xxxxxxxxxxxxxxx; christoffer.dall@xxxxxxxxxx; marc.zyngier@xxxxxxx;
> >> alex.williamson@xxxxxxxxxx; pbonzini@xxxxxxxxxx; avi.kivity@xxxxxxxxx;
> >> mtosatti@xxxxxxxxxx; Wu, Feng; joro@xxxxxxxxxx;
> >> b.reynal@xxxxxxxxxxxxxxxxxxxxxx
> >> Cc: linux-kernel@xxxxxxxxxxxxxxx; patches@xxxxxxxxxx
> >> 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@xxxxxxxxxx>
> >> ---
> >>  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
> >

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