linux-kernel - Re: [v5 15/19] KVM: eventfd: add irq bypass consumer management

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Date:	Mon, 13 Jul 2015 15:16:29 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Feng Wu <feng.wu@...el.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
CC:	pbonzini@...hat.com, alex.williamson@...hat.com, joro@...tes.org
Subject: Re: [v5 15/19] KVM: eventfd: add irq bypass consumer management

Hi Feng,
On 07/13/2015 11:47 AM, Feng Wu wrote:
> From: Eric Auger <eric.auger@...aro.org>
> 
> This patch adds the registration/unregistration of an
> irq_bypass_consumer on irqfd assignment/deassignment.
> 
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> Signed-off-by: Feng Wu <feng.wu@...el.com>
> ---
>  virt/kvm/eventfd.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index 647ffb8..4225eea 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -35,6 +35,7 @@
>  #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>
> @@ -140,6 +141,7 @@ irqfd_shutdown(struct work_struct *work)
>  	/*
>  	 * It is now safe to release the object's resources
>  	 */
> +	irq_bypass_unregister_consumer(&irqfd->consumer);
>  	eventfd_ctx_put(irqfd->eventfd);
>  	kfree(irqfd);
>  }
> @@ -380,6 +382,11 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
>  	 */
>  	fdput(f);
>  
> +	irqfd->consumer.token = (void *)irqfd->eventfd;
> +	kvm_arch_irq_consumer_init(&irqfd->consumer);
what if the architecture does not implement kvm_arch_irq_consumer_init?

Also you are using here this single function kvm_arch_irq_consumer_init
to do some irq bypass manager settings + attaching your
irqfd->arch_update cb which does not really relate to IRQ bypass
manager. I think I preferred the approach where start/top/add/del were
exposed separately ([RFC v2 5/6] KVM: introduce kvm_arch functions for
IRQ bypass).

Why not adding another kvm_arch_irq_routing_update then, not necessarily
linked to irq bypass manager.

Best Regards

Eric
> +	ret = irq_bypass_register_consumer(&irqfd->consumer);
> +	WARN_ON(ret);
> +
>  	return 0;
>  
>  fail:
> 

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