On Mon, Nov 21, 2022 at 04:40:16PM +0000, Michael Kelley (LINUX) wrote:

As discussed in a parallel thread [1], the incorrect code here doesn't have
any real impact in already released Linux kernels.  It only affects the
transition that my patch series implements to change the way vTOM
is handled.

Are you sure?

PHYSICAL_PAGE_MASK is controlled by __PHYSICAL_MASK which is determined
by CONFIG_DYNAMIC_PHYSICAL_MASK and __PHYSICAL_MASK_SHIFT which all
differ depending on configurations and also dynamic.

It is probably still ok, in probably all possible cases even though I
wouldn't bet on it.

And this fix is simple and all clear so lemme ask it differently: what
would be any downsides in backporting it to stable, just in case?

I don't know what the tradeoffs are for backporting a fix that doesn't solve
a real problem vs. just letting it be.  Every backport carries some overhead
in the process

Have you seen the deluge of stable fixes? :-)

and there's always a non-zero risk of breaking something.

I don't see how this one would cause any breakage...

I've leaned away from adding the "Fixes:" tag in such cases. But if
it's better to go ahead and add the "Fixes:" tag for what's only a
theoretical problem, I'm OK with doing so.

I think this is a good to have fix anyway as it is Obviously
Correct(tm).

Unless you have any reservations you haven't shared yet...

[1] https://lkml.org/lkml/2022/11/11/1348

Btw, the proper way to reference to a mail message now is simply to do:

https://lore.kernel.org/r/<Message-ID>

as long as it has been posted on some ML which lore archives. And I
think it archives all.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette