Re: [PATCH v3] io: add io_pgtable abstraction

[Alice Ryhl <aliceryhl@google.com>]

On Wed, Nov 12, 2025 at 09:57:09AM -0300, Daniel Almeida wrote:
> Hi Alice,
> 
> > On 12 Nov 2025, at 07:15, Alice Ryhl <aliceryhl@google.com> wrote:
> > +    /// Map a physically contiguous range of pages of the same size.
> > +    ///
> > +    /// # Safety
> > +    ///
> > +    /// * This page table must not contain any mapping that overlaps with the mapping created by
> > +    ///   this call.
> 
> I don't think there is a restriction that forbids you from mapping a region that has already been mapped.
> 
> If A->B->C are adjacent regions, and you try to map A -> C when B->C is already mapped, I think this
> call will simply return length(A->B).

I think that such overlapping ranges are not allowed. It triggers a
warn:

        } else if (pte) {                                                           
                /* We require an unmap first */                                 
                WARN_ON(!(cfg->quirks & IO_PGTABLE_QUIRK_NO_WARN));             
                return -EEXIST;

Alice