KAISER: kexec triggers a warning

KAISER: kexec triggers a warning

[Juerg Haefliger]

[-- Attachment #1.1: Type: text/plain, Size: 3209 bytes --]

Loading a kexec kernel using today's linux-tip master with KAISER=y
triggers the following warning:

[   18.054017] ------------[ cut here ]------------
[   18.054024] WARNING: CPU: 0 PID: 1183 at
./arch/x86/include/asm/pgtable_64.h:258 native_set_p4d+0x5f/0x80
[   18.054025] Modules linked in: nls_utf8 isofs ppdev nls_iso8859_1
kvm_intel kvm irqbypass input_leds serio_raw i2c_piix4 parport_pc
parport qemu_fw_cfg mac_hid 9p fscache ib_iser rdma_cm iw_cm ib_cm
ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi
9pnet_virtio 9pnet ip_tables x_tables autofs4 btrfs zstd_decompress
zstd_compress xxhash raid10 raid456 async_raid6_recov async_memcpy
async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath
linear cirrus ttm drm_kms_helper syscopyarea sysfillrect sysimgblt
fb_sys_fops psmouse virtio_blk virtio_net drm floppy pata_acpi
[   18.054047] CPU: 0 PID: 1183 Comm: kexec Not tainted 4.14.0-kaiser+ #2
[   18.054047] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1ubuntu1 04/01/2014
[   18.054048] task: ffff8a53f9d0ab80 task.stack: ffffaba640890000
[   18.054049] RIP: 0010:native_set_p4d+0x5f/0x80
[   18.054050] RSP: 0018:ffffaba640893e20 EFLAGS: 00010246
[   18.054051] RAX: 0000000038ac9063 RBX: 000000003ffda000 RCX:
000000003ffda000
[   18.054051] RDX: ffff8a53fd1f6ff8 RSI: 0000000038ac9063 RDI:
ffff8a53f71ba000
[   18.054051] RBP: 000000003ffda000 R08: 000075abc0000000 R09:
ffff8a53f8ac9000
[   18.054052] R10: 0000000000000003 R11: 000000003ffda000 R12:
ffff8a53f71ba000
[   18.054052] R13: ffffaba640893e78 R14: 0000000000000000 R15:
ffffff8000000000
[   18.054053] FS:  00007f0e95188740(0000) GS:ffff8a53ffc00000(0000)
knlGS:0000000000000000
[   18.054054] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   18.054054] CR2: 00007f0e94bf0fa0 CR3: 000000003c452000 CR4:
00000000000006f0
[   18.054056] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[   18.054056] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[   18.054057] Call Trace:
[   18.054065]  kernel_ident_mapping_init+0x147/0x190
[   18.054069]  machine_kexec_prepare+0xc8/0x490
[   18.054071]  ? trace_clock_x86_tsc+0x10/0x10
[   18.054074]  do_kexec_load+0x1d7/0x2d0
[   18.054079]  SyS_kexec_load+0x84/0xc0
[   18.054083]  entry_SYSCALL_64_fastpath+0x1e/0x81
[   18.054087] RIP: 0033:0x7f0e94c9c9f9
[   18.054087] RSP: 002b:00007ffe0d1a83e8 EFLAGS: 00000246 ORIG_RAX:
00000000000000f6
[   18.054088] RAX: ffffffffffffffda RBX: 000055a491d71240 RCX:
00007f0e94c9c9f9
[   18.054089] RDX: 000055a492aaa570 RSI: 0000000000000003 RDI:
000000003ffd1730
[   18.054089] RBP: 00007ffe0d1a8510 R08: 0000000000000008 R09:
0000000000000001
[   18.054089] R10: 00000000003e0000 R11: 0000000000000246 R12:
0000000000000100
[   18.054090] R13: 0000000000000040 R14: 0000000001b1d820 R15:
000000000007c7e0
[   18.054090] Code: 37 c3 f6 07 04 74 1b 48 89 f8 25 ff 0f 00 00 48 3d
ff 07 00 00 77 18 48 89 f8 80 cc 10 48 89 30 eb dc 83 3d 07 6d ff 00 02
75 d3 <0f> ff eb cf 0f ff eb cb 48 b8 00 00 00 00 00 00 00 80 48 09 c6
[   18.054104] ---[ end trace f206deb161cf8af0 ]---

...Juerg


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Re: KAISER: kexec triggers a warning

[Baoquan He]

On 12/01/17 at 02:52pm, Juerg Haefliger wrote:
> Loading a kexec kernel using today's linux-tip master with KAISER=y
> triggers the following warning:

I also noticed this when trigger a crash to jump to kdump kernel, and
kdump kernel failed to bootup. I am trying to fix it on tip/WIP.x86/mm.
Maybe still need a little time.

> 
> [   18.054017] ------------[ cut here ]------------
> [   18.054024] WARNING: CPU: 0 PID: 1183 at
> ./arch/x86/include/asm/pgtable_64.h:258 native_set_p4d+0x5f/0x80
> [   18.054025] Modules linked in: nls_utf8 isofs ppdev nls_iso8859_1
> kvm_intel kvm irqbypass input_leds serio_raw i2c_piix4 parport_pc
> parport qemu_fw_cfg mac_hid 9p fscache ib_iser rdma_cm iw_cm ib_cm
> ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi
> 9pnet_virtio 9pnet ip_tables x_tables autofs4 btrfs zstd_decompress
> zstd_compress xxhash raid10 raid456 async_raid6_recov async_memcpy
> async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath
> linear cirrus ttm drm_kms_helper syscopyarea sysfillrect sysimgblt
> fb_sys_fops psmouse virtio_blk virtio_net drm floppy pata_acpi
> [   18.054047] CPU: 0 PID: 1183 Comm: kexec Not tainted 4.14.0-kaiser+ #2
> [   18.054047] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.10.2-1ubuntu1 04/01/2014
> [   18.054048] task: ffff8a53f9d0ab80 task.stack: ffffaba640890000
> [   18.054049] RIP: 0010:native_set_p4d+0x5f/0x80
> [   18.054050] RSP: 0018:ffffaba640893e20 EFLAGS: 00010246
> [   18.054051] RAX: 0000000038ac9063 RBX: 000000003ffda000 RCX:
> 000000003ffda000
> [   18.054051] RDX: ffff8a53fd1f6ff8 RSI: 0000000038ac9063 RDI:
> ffff8a53f71ba000
> [   18.054051] RBP: 000000003ffda000 R08: 000075abc0000000 R09:
> ffff8a53f8ac9000
> [   18.054052] R10: 0000000000000003 R11: 000000003ffda000 R12:
> ffff8a53f71ba000
> [   18.054052] R13: ffffaba640893e78 R14: 0000000000000000 R15:
> ffffff8000000000
> [   18.054053] FS:  00007f0e95188740(0000) GS:ffff8a53ffc00000(0000)
> knlGS:0000000000000000
> [   18.054054] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   18.054054] CR2: 00007f0e94bf0fa0 CR3: 000000003c452000 CR4:
> 00000000000006f0
> [   18.054056] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [   18.054056] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400
> [   18.054057] Call Trace:
> [   18.054065]  kernel_ident_mapping_init+0x147/0x190
> [   18.054069]  machine_kexec_prepare+0xc8/0x490
> [   18.054071]  ? trace_clock_x86_tsc+0x10/0x10
> [   18.054074]  do_kexec_load+0x1d7/0x2d0
> [   18.054079]  SyS_kexec_load+0x84/0xc0
> [   18.054083]  entry_SYSCALL_64_fastpath+0x1e/0x81
> [   18.054087] RIP: 0033:0x7f0e94c9c9f9
> [   18.054087] RSP: 002b:00007ffe0d1a83e8 EFLAGS: 00000246 ORIG_RAX:
> 00000000000000f6
> [   18.054088] RAX: ffffffffffffffda RBX: 000055a491d71240 RCX:
> 00007f0e94c9c9f9
> [   18.054089] RDX: 000055a492aaa570 RSI: 0000000000000003 RDI:
> 000000003ffd1730
> [   18.054089] RBP: 00007ffe0d1a8510 R08: 0000000000000008 R09:
> 0000000000000001
> [   18.054089] R10: 00000000003e0000 R11: 0000000000000246 R12:
> 0000000000000100
> [   18.054090] R13: 0000000000000040 R14: 0000000001b1d820 R15:
> 000000000007c7e0
> [   18.054090] Code: 37 c3 f6 07 04 74 1b 48 89 f8 25 ff 0f 00 00 48 3d
> ff 07 00 00 77 18 48 89 f8 80 cc 10 48 89 30 eb dc 83 3d 07 6d ff 00 02
> 75 d3 <0f> ff eb cf 0f ff eb cb 48 b8 00 00 00 00 00 00 00 80 48 09 c6
> [   18.054104] ---[ end trace f206deb161cf8af0 ]---
> 
> ...Juerg
> 

Re: KAISER: kexec triggers a warning

[Borislav Petkov]

On Fri, Dec 01, 2017 at 11:18:51PM +0800, Baoquan He wrote:
> On 12/01/17 at 02:52pm, Juerg Haefliger wrote:
> > Loading a kexec kernel using today's linux-tip master with KAISER=y
> > triggers the following warning:
> 
> I also noticed this when trigger a crash to jump to kdump kernel, and
> kdump kernel failed to bootup. I am trying to fix it on tip/WIP.x86/mm.
> Maybe still need a little time.

Save yourself the energy, the WARN is wrong there and wil go away.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: KAISER: kexec triggers a warning

[Dave Hansen]

On 12/01/2017 05:52 AM, Juerg Haefliger wrote:
> Loading a kexec kernel using today's linux-tip master with KAISER=y
> triggers the following warning:
> 
> [   18.054017] ------------[ cut here ]------------
> [   18.054024] WARNING: CPU: 0 PID: 1183 at
> ./arch/x86/include/asm/pgtable_64.h:258 native_set_p4d+0x5f/0x80
> [   18.054025] Modules linked in: nls_utf8 isofs ppdev nls_iso8859_1
> kvm_intel kvm irqbypass input_leds serio_raw i2c_piix4 parport_pc
> parport qemu_fw_cfg mac_hid 9p fscache ib_iser rdma_cm iw_cm ib_cm

This is kexec is messing with PTEs that map the kernel, which is OK for
kexec to do.  The warning is harmless.

The only question is whether we want to preserve _some_ kind of warning
there, or just axe it entirely.

Re: KAISER: kexec triggers a warning

[Borislav Petkov]

On Fri, Dec 01, 2017 at 07:31:36AM -0800, Dave Hansen wrote:
> The only question is whether we want to preserve _some_ kind of warning
> there, or just axe it entirely.

Right, my fear would be if we keep it, then we'd have to go and
whitelist or somehow track those users which are an exception...

OTOH, it might be prudent to have a warning to catch such abnormal
situations...

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: KAISER: kexec triggers a warning

[Eduardo Valentin]

On Fri, Dec 01, 2017 at 04:37:13PM +0100, Borislav Petkov wrote:
> On Fri, Dec 01, 2017 at 07:31:36AM -0800, Dave Hansen wrote:
> > The only question is whether we want to preserve _some_ kind of warning
> > there, or just axe it entirely.
> 
> Right, my fear would be if we keep it, then we'd have to go and
> whitelist or somehow track those users which are an exception...
> 
> OTOH, it might be prudent to have a warning to catch such abnormal
> situations...

But a warn like that on the kexec/kdump path can be scary for regular / unware users,
specially considering that kexec is almost common place for regular reboot.

> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.
> 

-- 
All the best,
Eduardo Valentin

Re: KAISER: kexec triggers a warning

[Borislav Petkov]

On Fri, Dec 01, 2017 at 08:38:50AM -0800, Eduardo Valentin wrote:
> But a warn like that on the kexec/kdump path can be scary for regular
> / unware users, specially considering that kexec is almost common
> place for regular reboot.

... thus the whitelisting/tracking/... of legitimate users so that we
warn only for the abnormal cases.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: KAISER: kexec triggers a warning

[Baoquan He]

On 12/01/17 at 04:27pm, Borislav Petkov wrote:
> On Fri, Dec 01, 2017 at 11:18:51PM +0800, Baoquan He wrote:
> > On 12/01/17 at 02:52pm, Juerg Haefliger wrote:
> > > Loading a kexec kernel using today's linux-tip master with KAISER=y
> > > triggers the following warning:
> > 
> > I also noticed this when trigger a crash to jump to kdump kernel, and
> > kdump kernel failed to bootup. I am trying to fix it on tip/WIP.x86/mm.
> > Maybe still need a little time.
> 
> Save yourself the energy, the WARN is wrong there and wil go away.

OK, will test patch.

> -- 
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.