Remove WARN_ONCE for unaligned UEFI region?

[Ard Biesheuvel]

On Sun, 6 Nov 2022 at 03:29, Heinrich Schuchardt
<heinrich.schuchardt at canonical.com> wrote:
>
>
>
> On 11/5/22 23:43, Ard Biesheuvel wrote:
> > On Sat, 5 Nov 2022 at 22:54, Ard Biesheuvel <ardb at kernel.org> wrote:
> >>
> >> (cc Heinrich and Ilias)
> >>
> >> On Sat, 5 Nov 2022 at 21:27, Linus Torvalds
> >> <torvalds at linux-foundation.org> wrote:
> >>>
> >>> On Sat, Nov 5, 2022 at 1:18 PM Ard Biesheuvel <ardb at kernel.org> wrote:
> >>>>
> >>>> Yeah just rip it out. In the beginning, we tended to make these
> >>>> warnings noisy so people will actually notice.
> >>>
> >>> Rip it out entirely, or replace ith pr_warn_once()?
> >>>
> >>
> >> A warning that can only trigger on 16k or 64k page size kernels
> >> clearly doesn't have a lot of coverage, so either we just drop it, or
> >> we make the warning use SZ_64K and not PAGE_SIZE.
> >>
> >> And if we keep the warning, it should be separate from the if(): when
> >> the regions are misaligned, we have to use RWX mappings because an
> >> adjacent region that gets covered by the same mapping might require
> >> it.
> >>
> >> Maybe I'll just whip up a patch myself.
> >>
> >>>> I'd still like to see a memory map (boot with efi=debug) so we can get
> >>>> this reported and fixed in uboot. We need that so 16k and 64k pages
> >>>> boot doesn't cause surprises with overlapping mappings.
> >>>
> >>> Here's the dmesg attached with efi=debug for your viewing pleasure.
> >>>
> >>
> >> Thanks.
> >>
> >> I've cc'ed the u-boot EFI maintainers, who take EFI spec compliance
> >> very seriously, so I'm sure we'll get this fixed quickly.
> >
> > Grrr looking at the spec, it seems the wording we proposed at the time
> > never made it in, and at the moment, it just reads:
>
> Could you, please, provide a link to the proposal.
>

No, I cannot, unfortunately. This was almost 10 years ago, and I was
at Linaro at the time. In the mean time, they have wiped my account.

But to be honest, I might be misremembering. This was before we had
the memory attributes table, and during the development of that, this
topic also came back.

In any case, let's use today's spec as a starting point for refining this.