linux-kernel - Re: mm/pgtable: add stubs for {pmd/pub}_{set/clear}

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Date:   Wed, 14 Jul 2021 09:52:22 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Anshuman Khandual <anshuman.khandual@....com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge

(added Anshuman)

On Tue, Jul 13, 2021 at 04:39:25PM +0200, Geert Uytterhoeven wrote:
> Hi Christophe,
> 
> On Fri, Jul 2, 2021 at 10:16 PM Linux Kernel Mailing List
> <linux-kernel@...r.kernel.org> wrote:
> > Commit:     c742199a014de23ee92055c2473d91fe5561ffdf
> > Parent:     79c1c594f49a88fba9744cb5c85978c6b1b365ec
> > Refname:    refs/heads/master
> > Web:        https://git.kernel.org/torvalds/c/c742199a014de23ee92055c2473d91fe5561ffdf
> > Author:     Christophe Leroy <christophe.leroy@...roup.eu>
> > AuthorDate: Wed Jun 30 18:48:03 2021 -0700
> > Committer:  Linus Torvalds <torvalds@...ux-foundation.org>
> > CommitDate: Wed Jun 30 20:47:26 2021 -0700
> >
> >     mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge
> >
> >     For architectures with no PMD and/or no PUD, add stubs similar to what we
> >     have for architectures without P4D.
> >
> >     [christophe.leroy@...roup.eu: arm64: define only {pud/pmd}_{set/clear}_huge when useful]
> >       Link: https://lkml.kernel.org/r/73ec95f40cafbbb69bdfb43a7f53876fd845b0ce.1620990479.git.christophe.leroy@csgroup.eu
> >     [christophe.leroy@...roup.eu: x86: define only {pud/pmd}_{set/clear}_huge when useful]
> >       Link: https://lkml.kernel.org/r/7fbf1b6bc3e15c07c24fa45278d57064f14c896b.1620930415.git.christophe.leroy@csgroup.eu
> >
> >     Link: https://lkml.kernel.org/r/5ac5976419350e8e048d463a64cae449eb3ba4b0.1620795204.git.christophe.leroy@csgroup.eu
> >     Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> >     Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> >     Cc: Michael Ellerman <mpe@...erman.id.au>
> >     Cc: Mike Kravetz <mike.kravetz@...cle.com>
> >     Cc: Mike Rapoport <rppt@...nel.org>
> >     Cc: Nicholas Piggin <npiggin@...il.com>
> >     Cc: Paul Mackerras <paulus@...ba.org>
> >     Cc: Uladzislau Rezki <uladzislau.rezki@...y.com>
> >     Cc: Naresh Kamboju <naresh.kamboju@...aro.org>
> >     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> >     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> 
> Since this commit, both WARN_ON() tests in pud_huge_tests() are
> triggering on arm64 if CONFIG_ARM64_VA_BITS_39=y and
> CONFIG_PGTABLE_LEVELS=3:
> 
>     ------------[ cut here ]------------
>     WARNING: CPU: 0 PID: 1 at mm/debug_vm_pgtable.c:438
> debug_vm_pgtable+0x6d0/0x7c4
>     Modules linked in:
>     CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> 5.13.0-salvator-x-00209-gc742199a014d #1068
>     Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
>     pstate: a0400005 (NzCv daif +PAN -UAO -TCO BTYPE=--)
>     pc : debug_vm_pgtable+0x6d0/0x7c4
>     lr : debug_vm_pgtable+0x6cc/0x7c4
>     sp : ffffffc0124cbd00
>     x29: ffffffc0124cbd00 x28: 0000000000000c30 x27: ffffff84c5e465a0
>     x26: ffffff84c5e46000 x25: ffffff84c5e42000 x24: 00000000000005a0
>     x23: ffffffc010c41000 x22: 0020000050cb0fc3 x21: ffffff84c5e45ed0
>     x20: ffffff84c27470a8 x19: ffffff84c2747040 x18: 0000000000000cc0
>     x17: 00000000b2491cf5 x16: 0000000000000014 x15: 0000000000000000
>     x14: 0000000000000002 x13: 00000000000b56dd x12: 0000000000000901
>     x11: ffffffc01116d040 x10: 00000000000038e4 x9 : 00000000ffffffff
>     x8 : 0000000000000000 x7 : ffffffc010cc4cd0 x6 : 0000000000000000
>     x5 : 000000000004028e x4 : 0000000000000000 x3 : 0000000000000000
>     x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff84c08bc040
>     Call trace:
>      debug_vm_pgtable+0x6d0/0x7c4
>      do_one_initcall+0xec/0x278
>      kernel_init_freeable+0x220/0x224
>      kernel_init+0x10/0x108
>      ret_from_fork+0x10/0x18
>     irq event stamp: 1062694
>     hardirqs last  enabled at (1062693): [<ffffffc0101bb030>]
> free_unref_page+0x120/0x138
>     hardirqs last disabled at (1062694): [<ffffffc01085f31c>] el1_dbg+0x24/0x4c
>     softirqs last  enabled at (1062636): [<ffffffc0100101c8>] _stext+0x1c8/0x43c
>     softirqs last disabled at (1062627): [<ffffffc010080020>]
> __irq_exit_rcu+0xdc/0x124
>     ---[ end trace 864024bcea12ea00 ]---
>     ------------[ cut here ]------------
>     WARNING: CPU: 0 PID: 1 at mm/debug_vm_pgtable.c:439
> debug_vm_pgtable+0x6d4/0x7c4
>     Modules linked in:
>     CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W
> 5.13.0-salvator-x-00209-gc742199a014d #1068
>     Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
>     pstate: a0400005 (NzCv daif +PAN -UAO -TCO BTYPE=--)
>     pc : debug_vm_pgtable+0x6d4/0x7c4
>     lr : debug_vm_pgtable+0x6cc/0x7c4
>     sp : ffffffc0124cbd00
>     x29: ffffffc0124cbd00 x28: 0000000000000c30 x27: ffffff84c5e465a0
>     x26: ffffff84c5e46000 x25: ffffff84c5e42000 x24: 00000000000005a0
>     x23: ffffffc010c41000 x22: 0020000050cb0fc3 x21: ffffff84c5e45ed0
>     x20: ffffff84c27470a8 x19: ffffff84c2747040 x18: 0000000000000cc0
>     x17: 00000000b2491cf5 x16: 0000000000000014 x15: 0000000000000000
>     x14: 0000000000000002 x13: 00000000000b56dd x12: 0000000000000901
>     x11: ffffffc01116d040 x10: 00000000000038e4 x9 : 00000000ffffffff
>     x8 : 0000000000000000 x7 : ffffffc010cc4cd0 x6 : 0000000000000000
>     x5 : 000000000004028e x4 : 0000000000000000 x3 : 0000000000000000
>     x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff84c08bc040
>     Call trace:
>      debug_vm_pgtable+0x6d4/0x7c4
>      do_one_initcall+0xec/0x278
>      kernel_init_freeable+0x220/0x224
>      kernel_init+0x10/0x108
>      ret_from_fork+0x10/0x18
>     irq event stamp: 1062706
>     hardirqs last  enabled at (1062705): [<ffffffc01085ef80>]
> exit_to_kernel_mode+0xf0/0x100
>     hardirqs last disabled at (1062706): [<ffffffc01085f31c>] el1_dbg+0x24/0x4c
>     softirqs last  enabled at (1062704): [<ffffffc0100101c8>] _stext+0x1c8/0x43c
>     softirqs last disabled at (1062697): [<ffffffc010080020>]
> __irq_exit_rcu+0xdc/0x124
>     ---[ end trace 864024bcea12ea01 ]---
> 
> Switching to CONFIG_ARM64_VA_BITS_48=y and CONFIG_PGTABLE_LEVELS=4
> makes the warning disappear.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

-- 
Sincerely yours,
Mike.