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

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Date:	Mon, 06 Jul 2015 13:19:46 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	"Wu, Feng" <feng.wu@...el.com>,
	"eric.auger@...com" <eric.auger@...com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	"marc.zyngier@....com" <marc.zyngier@....com>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"avi.kivity@...il.com" <avi.kivity@...il.com>,
	"mtosatti@...hat.com" <mtosatti@...hat.com>,
	"joro@...tes.org" <joro@...tes.org>,
	"b.reynal@...tualopensystems.com" <b.reynal@...tualopensystems.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"patches@...aro.org" <patches@...aro.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@...aro.org]
>> Sent: Thursday, July 02, 2015 9:17 PM
>> To: eric.auger@...com; eric.auger@...aro.org;
>> linux-arm-kernel@...ts.infradead.org; kvmarm@...ts.cs.columbia.edu;
>> kvm@...r.kernel.org; christoffer.dall@...aro.org; marc.zyngier@....com;
>> alex.williamson@...hat.com; pbonzini@...hat.com; avi.kivity@...il.com;
>> mtosatti@...hat.com; Wu, Feng; joro@...tes.org;
>> b.reynal@...tualopensystems.com
>> Cc: linux-kernel@...r.kernel.org; patches@...aro.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@...aro.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
> 

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