linux-kernel - Re: [PATCHv2 6/8] x86/dump_pagetables: Add support 5-level paging

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Date:   Tue, 28 Mar 2017 20:55:22 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 6/8] x86/dump_pagetables: Add support 5-level paging

On Tue, Mar 28, 2017 at 01:48:06PM +0300, Kirill A. Shutemov wrote:
> Simple extension to support one more page table level.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/x86/mm/dump_pagetables.c | 59 +++++++++++++++++++++++++++++++++----------
>  1 file changed, 45 insertions(+), 14 deletions(-)

Hmm, so without this I get the splat below.

Can we do something about this bisection breakage? I mean, this is the
second explosion caused by 5level paging I trigger. Maybe we should
merge the whole thing into a single big patch when everything is applied
and tested, more or less, so that bisection is fine.

Or someone might have a better idea...

[    2.801262] BUG: unable to handle kernel paging request at ffffc753f000f000
[    2.803013] IP: ptdump_walk_pgd_level_core+0x236/0x3a0
[    2.804472] PGD 0 
[    2.804473] P4D 0 
[    2.805231] 
[    2.805231] Oops: 0000 [#1] PREEMPT SMP
[    2.805231] Modules linked in:
[    2.805231] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc4+ #1
[    2.805231] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[    2.805231] task: ffff88007c1c8040 task.stack: ffffc90000008000
[    2.805231] RIP: 0010:ptdump_walk_pgd_level_core+0x236/0x3a0
[    2.805231] RSP: 0018:ffffc9000000be48 EFLAGS: 00010256
[    2.805231] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[    2.805231] RDX: ffff880000001000 RSI: ffff880000000000 RDI: ffffc9000000bed0
[    2.805231] RBP: ffffc9000000bef8 R08: 0000000000000000 R09: 000000000000017f
[    2.805231] R10: 000000000000001f R11: 0000000000000001 R12: ffffc9000000be90
[    2.805231] R13: 0000000000000000 R14: ffffc753f000f000 R15: 00000000ffffff00
[    2.805231] FS:  0000000000000000(0000) GS:ffff88007ed00000(0000) knlGS:0000000000000000
[    2.805231] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.805231] CR2: ffffc753f000f000 CR3: 0000000001c09000 CR4: 00000000000406e0
[    2.805231] Call Trace:
[    2.805231]  ? 0xffffffff81000000
[    2.805231]  ptdump_walk_pgd_level_checkwx+0x17/0x20
[    2.805231]  mark_rodata_ro+0xec/0x100
[    2.805231]  ? rest_init+0x90/0x90
[    2.805231]  kernel_init+0x2a/0x100
[    2.805231]  ret_from_fork+0x2e/0x40
[    2.805231] Code: 00 88 ff ff 48 8b 5d 88 4c 8d 34 10 48 ba 00 10 00 00 00 88 ff ff 48 01 d0 48 89 85 70 ff ff ff 48 89 d8 48 c1 f8 10 48 89 45 b0 <49> 8b 06 48 a9 9f ff ff ff 74 7c 48 89 c1 48 be ff 0f 00 00 00 
[    2.805231] RIP: ptdump_walk_pgd_level_core+0x236/0x3a0 RSP: ffffc9000000be48
[    2.805231] CR2: ffffc753f000f000
[    2.805231] ---[ end trace 3ec6e2c757df799d ]---
[    2.805231] Kernel panic - not syncing: Fatal exception
[    2.805231] Kernel Offset: disabled
[    2.805231] ---[ end Kernel panic - not syncing: Fatal exception

-- 
Regards/Gruss,
    Boris.

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