Re: [PATCH net-next 2/3] mm: vmalloc: export find_vm_area()

[Jason Gunthorpe]

On Wed, Jan 28, 2026 at 11:45:58AM +0800, D. Wythe wrote:

> By leveraging vmalloc_huge() and the proposed helper to increase the
> page_size in ib_map_mr_sg(), each MTTE covers a much larger contiguous
> physical block.

This doesn't seem right, if your goal is to take a vmalloc() pointer
and convert it to a MR via a scatterlist and ib_map_mr_sg() then you
should be asking for a helper to convert a kernel pointer into a
scatterlist.

Even if you do this in a naive way and call the
sg_alloc_append_table_from_pages() function it will automatically join
physically contiguous ranges together for you.

>From there you can check the resulting scatterlist and compute the
page_size to pass to ib_map_mr_sg().

No need to ask the MM for anything other than the list of physicals to
build the scatterlist with.

Still, I wouldn't mind seeing a helper to convert a kernel pointer
into a scatterlist because I have see that opencoded in a few places,
and maybe there are ways to optimize that using more information from
the MM - but it should be APIs used only by this helper not exposed to
drivers.

Jason