Re: [PATCH] iommu/amd: Fix ineffective error check in nested domain allocation

[Vasant Hegde]

On 8/25/2026 3:35 PM, Hemanth Selam wrote:
> 
> amd_iommu_pdom_id_alloc() returns an int: a domain ID on success, or the
> negative errno from ida_alloc_range() when the ID space is exhausted or
> memory is short.  amd_iommu_alloc_domain_nested() stores that return value
> in gdom_info->hdom_id, which is a u32, and only then tests it:
> 
>         gdom_info->hdom_id = amd_iommu_pdom_id_alloc();
>         if (gdom_info->hdom_id <= 0) {
> 
> The assignment discards the sign, so -ENOSPC becomes 0xffffffe4 and the
> test never fires.  The nested domain is then set up with a host domain ID
> that was never allocated, instead of the allocation failing with -ENOSPC.
> 
> Keep the value in an int, test it there, and store it only once it is
> known to be valid, which is what the other amd_iommu_pdom_id_alloc()
> callers already do.
> 
> Fixes: 757d2b1fdf5b ("iommu/amd: Introduce gDomID-to-hDomID Mapping and handle parent domain invalidation")
> Signed-off-by: Hemanth Selam <hemanth.selam@xxxxxxxxx>

Reviewed-by: Vasant Hegde <vasant.hegde@xxxxxxx>

-Vasant