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

Andre Przywara
2017-10-06T14:37:14Z

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.

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;
> }
>