linux-kernel - Re: [tip:x86/mm] x86: Convert the rest of the code to support p4d

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Date:   Mon, 24 Apr 2017 19:57:57 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     dvlasenk@...hat.com, Ingo Molnar <mingo@...nel.org>,
        luto@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        brgerst@...il.com, Arnd Bergmann <arnd@...db.de>,
        jpoimboe@...hat.com, mhocko@...e.com,
        "H. Peter Anvin" <hpa@...or.com>, dave.hansen@...el.com,
        Peter Zijlstra <peterz@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86: Convert the rest of the code to support p4d_t

On Sun, Apr 23, 2017 at 12:56:14PM -0700, Dan Williams wrote:
> On Mon, Mar 27, 2017 at 3:25 AM, tip-bot for Kirill A. Shutemov
> <tipbot@...or.com> wrote:
> > Commit-ID:  f2a6a7050109e0a5c7a84c70aa6010f682b2f1ee
> > Gitweb:     http://git.kernel.org/tip/f2a6a7050109e0a5c7a84c70aa6010f682b2f1ee
> > Author:     Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > AuthorDate: Fri, 17 Mar 2017 21:55:15 +0300
> > Committer:  Ingo Molnar <mingo@...nel.org>
> > CommitDate: Mon, 27 Mar 2017 08:56:58 +0200
> >
> > x86: Convert the rest of the code to support p4d_t
> >
> > This patch converts x86 to use proper folding of a new (fifth) page table level
> > with <asm-generic/pgtable-nop4d.h>.
> >
> > That's a bit of a kitchen sink patch, but I don't see how to split it further
> > without hurting bisectability.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Acked-by: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Andy Lutomirski <luto@...capital.net>
> > Cc: Andy Lutomirski <luto@...nel.org>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: Brian Gerst <brgerst@...il.com>
> > Cc: Dave Hansen <dave.hansen@...el.com>
> > Cc: Denys Vlasenko <dvlasenk@...hat.com>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Michal Hocko <mhocko@...e.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: linux-arch@...r.kernel.org
> > Cc: linux-mm@...ck.org
> > Link: http://lkml.kernel.org/r/20170317185515.8636-7-kirill.shutemov@linux.intel.com
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> 
> Following Ingo's revert of commit 2947ba054a4d "x86/mm/gup: Switch GUP
> to the generic get_user_page_fast() implementation", I gave
> tip.git/master a try to see if it resolved the original failing
> signature I was seeing with the "device-dax" regression test [1] on
> next/master. It turns out that there are two failing signatures and I
> need to use the revert during the bisect to find this other
> regression. This new bisect points to commit f2a6a7050109 "x86:
> Convert the rest of the code to support p4d_t" as the culprit.
> 
> [   43.194330] BUG: unable to handle kernel paging request at ffff880300000000

I cannot reproduce the issue.

Could you share your kernel kernel config?

-- 
 Kirill A. Shutemov