Re: [PATCH 5/5] vfio/type1: Use mapping page mask for pfnmaps

From: Jason Gunthorpe
Date: Fri Feb 14 2025 - 14:27:15 EST


On Wed, Feb 05, 2025 at 04:17:21PM -0700, Alex Williamson wrote:
> @@ -590,15 +592,23 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,
> vma = vma_lookup(mm, vaddr);
>
> if (vma && vma->vm_flags & VM_PFNMAP) {
> - ret = follow_fault_pfn(vma, mm, vaddr, pfn, prot & IOMMU_WRITE);
> + unsigned long pgmask;
> +
> + ret = follow_fault_pfn(vma, mm, vaddr, pfn, &pgmask,
> + prot & IOMMU_WRITE);
> if (ret == -EAGAIN)
> goto retry;
>
> if (!ret) {
> - if (is_invalid_reserved_pfn(*pfn))
> - ret = 1;
> - else
> + if (is_invalid_reserved_pfn(*pfn)) {
> + unsigned long epfn;
> +
> + epfn = (((*pfn << PAGE_SHIFT) + ~pgmask + 1)
> + & pgmask) >> PAGE_SHIFT;

That seems a bit indirect

epfn = ((*pfn) | (~pgmask >> PAGE_SHIFT)) + 1;

?

> + ret = min_t(int, npages, epfn - *pfn);

It is nitty but the int's here should be long, and npages should be
unsigned long..

Jason