Re: [PATCH v2 1/2] iova: Remove some magazine pointer NULL checks

[John Garry]

On 06/09/2022 10:28, Ethan Zhao wrote:

Hi Ethan,

> > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> > Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
> > ---
> >   drivers/iommu/iova.c | 7 ++-----
> >   1 file changed, 2 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> > index 47d1983dfa2a..580fdf669922 100644
> > --- a/drivers/iommu/iova.c
> > +++ b/drivers/iommu/iova.c
> > @@ -661,9 +661,6 @@ iova_magazine_free_pfns(struct iova_magazine *mag, 
> > struct iova_domain *iovad)
> >       unsigned long flags;
> >       int i;
> > -    if (!mag)
> > -        return;
> > -
>
> iommu_probe_device
>    ops->probe_finalize(dev);
>      intel_iommu_probe_finalize
>         iommu_setup_dma_ops
>           iommu_dma_init_domain(domain, dma_base, dma_limit, dev)
>             iova_domain_init_rcaches
>               {
>               ...
>               cpu_rcache->loaded = iova_magazine_alloc(GFP_KERNEL);
>               cpu_rcache->prev = iova_magazine_alloc(GFP_KERNEL);
>             if (!cpu_rcache->loaded || !cpu_rcache->prev) {
>                  ret = -ENOMEM;
>                        goto out_err;
>
> Do you mean iova_magazine_alloc() is impossible to fail ?

No, iova_magazine_alloc() may fail and return NULL. But if it does then 
we set iovad rcache pointer = NULL in the error path and don't use the 
rcache.

However we have a !iovad->rcache check on the "fast" alloc but not 
"insert". I need to check why that is again.

Thanks,
john