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

[Auger Eric <eric.auger@redhat.com>]

Hi Andre,

On 06/10/2017 16:37, Andre Przywara wrote:
> Hi,
> 
> On 27/09/17 14:28, Eric Auger wrote:
>> From: wanghaibin <wanghaibin.wang@huawei.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.
>>
>> Signed-off-by: wanghaibin <wanghaibin.wang@huawei.com>
> 
> Looks right to me. But I wonder if we actually should go over the file
> and unify the return value semantics or at least document them.
> It's a bit puzzling to have functions which return negative errors and 0
> *or 1* on success, and then functions which go with the traditional C
> convention. That would help explaining the second hunk.
> 
> Also this return value handling is a bit weird in cases, like in
> handle_l1_dte():
> 
> 	if (ret <= 0)
> 		return ret;
> 	return 1;
> 
> which looks like a glorified "return ret;" in that case to me.
Yes that's sadly true.

Yep this error handling is a mess I must confess. I will try to better
document and unify as much as possible.

Thanks a lot for your review.

Eric
> 
> But actually this is just nitpicking and the actual patch seems correct.
> 
> Cheers,
> Andre.
> 
>> ---
>>
>> 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;
>>  }
>>