linux-kernel - Re: [PATCH v2 01/10] KVM: arm/arm64: vgic-its: fix return value for restore

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Date:   Fri, 13 Oct 2017 13:04:43 +0200
From:   Christoffer Dall <cdall@...aro.org>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, marc.zyngier@....com,
        peter.maydell@...aro.org, andre.przywara@....com,
        wanghaibin.wang@...wei.com, wu.wubin@...wei.com
Subject: Re: [PATCH v2 01/10] KVM: arm/arm64: vgic-its: fix return value for
 restore

On Wed, Sep 27, 2017 at 03:28:31PM +0200, Eric Auger wrote:
> From: wanghaibin <wanghaibin.wang@...wei.com>
> 
> This patch fix the migrate restore tables failure.
> 
> The same scene, at the destination, the restore tables
> interface traversal guest memory, and check the dte/ite
> is valid or not.  If all dtes/ites are invalid, we will do
> try next one, and the last it will take the 1 return value,
> but currently, it be treated as error. That's not correct.
> 
> This patch try to fix this problem.

This commit message really needs work.

> 
> Signed-off-by: wanghaibin <wanghaibin.wang@...wei.com>
> 
> ---
> 
> need to CC stable
> 
> v1 -> v2:
> - if (ret > 0) ret = 0
> ---
>  virt/kvm/arm/vgic/vgic-its.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index f51c1e1..fbbc97b 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -2018,7 +2018,7 @@ static int vgic_its_restore_dte(struct vgic_its *its, u32 id,
>  		return PTR_ERR(dev);
>  
>  	ret = vgic_its_restore_itt(its, dev);
> -	if (ret) {
> +	if (ret < 0) {
>  		vgic_its_free_device(its->dev->kvm, dev);
>  		return ret;
>  	}
> @@ -2141,7 +2141,7 @@ static int vgic_its_restore_device_tables(struct vgic_its *its)
>  	}
>  
>  	if (ret > 0)
> -		ret = -EINVAL;
> +		ret = 0;
>  
>  	return ret;
>  }
> -- 
> 2.5.5
> 

And I agree with the idea of cleaning up the return values.  I think it
could be improved by always returning 0 on some success and -ERR on some
error, and carry an additional return value is a parameter, indicating
if the last entry was found, which can be omitted (be NULL) by callers
who do not care.

Otherwise:
Acked-by: Christoffer Dall <christoffer.dall@...aro.org>