Re: [tip:x86/mm] x86: Convert the rest of the code to support p4d_t

[Dan Williams]

On Mon, Apr 24, 2017 at 9:57 AM, Kirill A. Shutemov
<kirill@xxxxxxxxxxxxx> wrote:
> 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@xxxxxxxxx> wrote:
>> > Commit-ID:  f2a6a7050109e0a5c7a84c70aa6010f682b2f1ee
>> > Gitweb:     http://git.kernel.org/tip/f2a6a7050109e0a5c7a84c70aa6010f682b2f1ee
>> > Author:     Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>> > AuthorDate: Fri, 17 Mar 2017 21:55:15 +0300
>> > Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
>> > 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@xxxxxxxxxxxxxxx>
>> > Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
>> > Cc: Andy Lutomirski <luto@xxxxxxxxxx>
>> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
>> > Cc: Borislav Petkov <bp@xxxxxxxxx>
>> > Cc: Brian Gerst <brgerst@xxxxxxxxx>
>> > Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
>> > Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
>> > Cc: H. Peter Anvin <hpa@xxxxxxxxx>
>> > Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
>> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>> > Cc: Michal Hocko <mhocko@xxxxxxxx>
>> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>> > Cc: linux-arch@xxxxxxxxxxxxxxx
>> > Cc: linux-mm@xxxxxxxxx
>> > Link: http://lkml.kernel.org/r/20170317185515.8636-7-kirill.shutemov@xxxxxxxxxxxxxxx
>> > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
>>
>> 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?

Kernel config available here:
https://gist.github.com/djbw/2b99a014396cca9f4406586573be98c0