From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCHv5 1/4] Provide userspace IO exit completion callback.
Date: Thu, 2 Aug 2012 16:26:29 -0300
Message-ID: <20120802192629.GA28613@amt.cnet>
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To: Gleb Natapov <gleb@redhat.com>
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On Mon, Jul 30, 2012 at 05:38:18PM +0300, Gleb Natapov wrote:
>  	int r;
> @@ -5554,9 +5568,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  		}
>  	}
>  
> -	r = complete_mmio(vcpu);
> -	if (r <= 0)
> -		goto out;
> +	if (unlikely(vcpu->arch.complete_userspace_io)) {
> +		int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io;
> +		vcpu->arch.complete_userspace_io = NULL;
> +		r = cui(vcpu);
> +		if (r <= 0)
> +			goto out;
> +	}

Would it be worthwhile to add BUG/WARN_ONs here checking for
variables that represent valid mmio/pio, but without
complete_userspace_io function pointer set? (you do that in 
the reverse case, inside the complete_userspace_io 
function pointers).