linux-kernel - Re: [PATCH 0/2] irqbypass/kvm: Silence registration errors

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Date:	Wed, 11 May 2016 16:49:59 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org
Cc:	feng.wu@...el.com, linux-kernel@...r.kernel.org,
	eric.auger@...aro.org
Subject: Re: [PATCH 0/2] irqbypass/kvm: Silence registration errors



On 05/05/2016 19:58, Alex Williamson wrote:
> Currently an AMD system using vfio-pci/kvm will issue a dev_info() for
> every MSI/X vector registered because kvm_x86_ops does not support a
> bypass mechanism except on Intel and the add_producer callback returns
> an errno for that.  This is meaningless, unintended, and confuses
> users.  We could simply have KVM's add_producer callback return 0 if
> there's no bypass mechanism, but then why are we registering as an IRQ
> bypass consumer in the first place?  We also don't necessarily want to
> simply remove the dev_info/pr_info on registration failure because
> then we have no warning if something does actually go wrong.  So
> instead, let's conditionalize IRQ bypass registration on whether we
> have any support for it, and to keep the de-registration path clean
> and fill an unintended gap, let's ignore deregistration of NULL tokens
> and prevent registration of the same.  NULL isn't a good, unique
> cookie anyway.  Tested on AMD and non-PI Intel.  Thanks,
> 
> Alex

Thanks, applying these patches to kvm/queue.

Paolo