linux-kernel - RE: [Patch v3 01/14] x86/ioremap: Fix page aligned size calculation in __ioremap

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Message-ID: <BYAPR21MB1688B18DD7FC0AFEBB945F41D70A9@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Mon, 21 Nov 2022 21:02:11 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Borislav Petkov <bp@...en8.de>
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Subject: RE: [Patch v3 01/14] x86/ioremap: Fix page aligned size calculation
 in __ioremap_caller()

From: Borislav Petkov <bp@...en8.de> Sent: Monday, November 21, 2022 11:45 AM
> 
> 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?

None

> 
> > 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...
> 

No reservations.   I'll add the "Fixes:" tag.

Michael