Re: [PATCH v2 03/16] iommu: Implement IOMMU domain preservation

[Samiullah Khawaja]

On Fri, May 01, 2026 at 10:08:47PM +0000, David Matlack wrote:
> On 2026-04-27 05:56 PM, Samiullah Khawaja wrote:
> > Add IOMMU domain ops that can be implemented by the IOMMU drivers if
> > they support IOMMU domain preservation across liveupdate. The new IOMMU
> > domain preserve, unpreserve and restore APIs call these ops to perform
> > respective live update operations.
> >
> > Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
>
> > +static int alloc_object_ser(struct iommu_array_hdr_ser **curr_array_ptr, u64 max_objs)
> > +{
> > +	struct iommu_array_hdr_ser *curr_array = *curr_array_ptr;
> > +	struct iommu_array_hdr_ser *next_array;
> > +
>
> There's a trade-off being made in this function to leak deleted array
> elements instead of trying to reuse them that warrants a comment.

Are you referring to the "deleted" flag in the HDR of each object? Yes
we don't look for deleted objects in linked-list of arrays and reuse
them for simplicity. I will add a comment that says this.
> > +	if (curr_array->nr_objects >= max_objs) {
> > +		next_array = kho_alloc_preserve(PAGE_SIZE);
> > +		if (IS_ERR(next_array))
> > +			return PTR_ERR(next_array);
> > +
> > +		curr_array->next_array_phys = virt_to_phys(next_array);
> > +		*curr_array_ptr = next_array;
> > +		curr_array = next_array;
> > +	}
> > +
> > +	return curr_array->nr_objects++;
> > +}