Re: [PATCH 4/5] mm: gup: Pass a pointer to virt_to_page()

Linus Walleij
2022-07-01T09:11:49Z

On Fri, Jul 1, 2022 at 2:29 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:

> On Thu, Jun 30, 2022 at 10:41:23AM +0200, Linus Walleij wrote:
> > Functions that work on a pointer to virtual memory such as
> > virt_to_pfn() and users of that function such as
> > virt_to_page() are supposed to pass a pointer to virtual
> > memory, ideally a (void *) or other pointer. However since
> > many architectures implement virt_to_pfn() as a macro,
> > this function becomes polymorphic and accepts both a
> > (unsigned long) and a (void *).
>
> I wonder if there is merit to convert x86 to use an inline after this
> goes in to prevent this polymorphic mistake?

I have a patch like that, x86 uses the asm generic version IIUC:
https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-integrator.git/patch/?id=ed4befbf783c06820e9d4620c7fd254a36d608fe

There was also Xen:
https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-integrator.git/patch/?id=43ab4e5d6738273055dca21031e23b53b3721889

The plan is to trickle in a few of those after I fixed up all the mm
and drivers that were doing this with unsigned longs.
I managed to convert all architectures except one to use
static inlines for virt_to_pfn.

I was actually a bit surprised how few sites there were.

Yours,
Linus Walleij