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

[John Garry]

On 07/09/2022 10:58, Ethan Zhao wrote:

Hi Ethan,

> > Or also add this:
> >
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index 0d6d8edf782d..e8f0b8f47f45 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -578,6 +578,12 @@ static int iommu_dma_init_domain(struct 
> > iommu_domain *domain, dma_addr_t base,
> >              goto done_unlock;
> >          }
> >
> > +        if (!iovad->rcaches) {
> > +            pr_warn("IOVA domain rcache not properly initialised\n");
> > +            ret = -EFAULT;
> > +            goto done_unlock;
> > +        }
> > +
> >          ret = 0;
> >          goto done_unlock;
> If the iovad->rcaches allocation failed, will skip iommu domain dma ops, 
> so no need *any* iovad,->rcaches check, right ?
>
> and there is already warning about the fallback.

It's not as simple as that. We use the iovad->start_pfn member as a flag 
for the IOVA domain being initialized. However that does not mean always 
properly initialized. As above, the rcache init may fail, but in this 
case we still set start_pfn.

This comes into play when we have multiple devices in the same IOMMU 
group, for example, as I mentioned yesterday.

Thanks,
John