Re: [PATCH v3] vfio/type1: Adopt fast IOTLB flush interface when unmap IOVAs

[Suravee Suthikulpanit]

Alex / Joerg,

On 1/24/18 5:04 AM, Alex Williamson wrote:
> > @@ -648,12 +685,40 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
> >   	return i > npage ? npage : (i > 0 ? i : -EINVAL);
> >   }
> >   
> > +static size_t try_unmap_unpin_fast(struct vfio_domain *domain, dma_addr_t iova,
> > +				   size_t len, phys_addr_t phys,
> > +				   struct list_head *unmapped_regions)
> > +{
> > +	struct vfio_regions *entry;
> > +	size_t unmapped;
> > +
> > +	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> > +	if (!entry)
> > +		return -ENOMEM;
> > +
> > +	unmapped = iommu_unmap_fast(domain->domain, iova, len);
> > +	if (WARN_ON(!unmapped)) {
> > +		kfree(entry);
> > +		return -EINVAL;
> > +	}
> Not sure about the handling of this, the zero check is just a
> consistency validation.  If there's nothing mapped where we think there
> should be something mapped, we warn and throw out the whole vfio_dma.
> After this patch, such an error gets warned twice, which doesn't
> really seem to be an improvement.

Since iommu_unmap() and iommu_unmap_fast() can return errors, instead of just zero check,
we should also check for errors, warn, and bail out the whole vfio_dma.

Thanks,
Suravee