RE: [PATCH v3 2/2] vfio/type1: Set IOMMU_MMIO in dma->prot for MMIO-backed addresses

[Tian, Kevin]

> From: Wei Wang <wei.w.wang@xxxxxxxxxxx>
> Sent: Thursday, November 13, 2025 11:54 PM
> 
> @@ -629,6 +630,8 @@ static long vaddr_get_pfns(struct mm_struct *mm,
> unsigned long vaddr,
>  				ret = -EFAULT;
>  			}
>  		}
> +		if (vma->vm_flags & VM_IO)
> +			*prot |= IOMMU_MMIO;

move into "if (is_invalid_reserved_pfn(*pfn)) {}". it's pointless to set
it in the error path.

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

btw another alternative is letting userspace set a map flag explicitly
e.g. introducing a new VFIO_DMA_MAP_FLAG_MMIO flag bit. It's
not considered because your use case requires existing VMMs to
work?