linux-kernel - Re: [GIT PULL] x86/mm changes for v5.9

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Date:   Thu, 13 Aug 2020 21:30:08 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/mm changes for v5.9


* Joerg Roedel <jroedel@...e.de> wrote:

> On Thu, Aug 06, 2020 at 11:20:19PM +0200, Ingo Molnar wrote:
> > I've reverted it in x86/urgent as well earlier today, can send you 
> > that tree right now if you prefer that route.
> 
> I sent a fix for preallocate_vmalloc_pages() to correctly pre-allocate
> the vmalloc PGD entries. I verified that it works and that
> swapper_pg_dir contains the correct entries now. This should also fix
> the issue Jason is seeing.

Thanks!

There's one thing left to do. Linus has reverted the patch which 
exposed this bug:

  7b4ea9456dd3: ("Revert "x86/mm/64: Do not sync vmalloc/ioremap mappings"")

and has applied your fix:

  995909a4e22b: ("x86/mm/64: Do not dereference non-present PGD entries")

I think now we can re-apply the original commit:

  8bb9bf242d1f: ("x86/mm/64: Do not sync vmalloc/ioremap mappings")

Mind re-sending it, with an updated changelog that explains why it's 
now truly safe?

Would be tentatively scheduled for v5.10 though, we've had enough 
excitement in this area for v5.9 I think. :-/

> Sorry for screwing this up :-(

No problem, and it was my fault too: I sent 8bb9bf242d1f to Linus too 
quickly, just 7 days after applying it - x86/mm patches usually need a 
few weeks of testing.

Thanks,

	Ingo