Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 13 Aug 2020 21:30:08 +0200
From:   Ingo Molnar <mingo@kernel.org>
To:     Joerg Roedel <jroedel@suse.de>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [GIT PULL] x86/mm changes for v5.9
Message-ID: <20200813193008.GB2338781@gmail.com>
References: <20200803190354.GA1293087@gmail.com>
 <20200805110348.GA108872@zx2c4.com>
 <CAHk-=wiq+7sW3Lk5iQ0-zY5XWES4rSxK505vXsgFY=za88+RZw@mail.gmail.com>
 <20200806131034.GA2067370@gmail.com>
 <20200806185723.GA24304@suse.de>
 <CAHk-=wg7PHCUMD1xY=YCCeVHspAhw0YNEhyO3CnHfRPwsf6P8A@mail.gmail.com>
 <20200806212019.GA2149204@gmail.com>
 <20200807084728.GA29510@suse.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200807084728.GA29510@suse.de>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


* Joerg Roedel <jroedel@suse.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