* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 6:30 [PATCH v3] xen: avoid crash in disable_hotplug_cpu Olaf Hering
@ 2018-09-07 7:48 ` Juergen Gross
2018-09-07 9:24 ` Olaf Hering
2018-09-07 9:24 ` Olaf Hering
2018-09-07 7:48 ` Juergen Gross
` (4 subsequent siblings)
5 siblings, 2 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-07 7:48 UTC (permalink / raw)
To: Olaf Hering, xen-devel; +Cc: Boris Ostrovsky, open list
On 07/09/18 08:30, Olaf Hering wrote:
> The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
> RIP: e030:device_offline+0x9/0xb0
> Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
> RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
> R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
> R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
> FS: 00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
> Call Trace:
> handle_vcpu_hotplug_event+0xb5/0xc0
> xenwatch_thread+0x80/0x140
> ? wait_woken+0x80/0x80
> kthread+0x112/0x130
> ? kthread_create_worker_on_cpu+0x40/0x40
> ret_from_fork+0x3a/0x50
>
> This happens because handle_vcpu_hotplug_event is called twice. In the
> first iteration cpu_present is still true, in the second iteration
> cpu_present is false which causes get_cpu_device to return NULL.
> In case of cpu#0, cpu_online is apparently always true.
>
> Fix this crash by checking if the cpu can be hotplugged, which is false
> for a cpu that was just removed.
>
> Also check if the cpu was actually offlined by device_remove, otherwise
> leave the cpu_present state as it is.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> ---
> drivers/xen/cpu_hotplug.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
> index d4265c8ebb22..68f9f663da08 100644
> --- a/drivers/xen/cpu_hotplug.c
> +++ b/drivers/xen/cpu_hotplug.c
> @@ -19,11 +19,15 @@ static void enable_hotplug_cpu(int cpu)
>
> static void disable_hotplug_cpu(int cpu)
> {
> + if (!cpu_is_hotpluggable(cpu))
> + return;
> if (cpu_online(cpu)) {
> lock_device_hotplug();
> device_offline(get_cpu_device(cpu));
> unlock_device_hotplug();
> }
> + if (cpu_online(cpu))
> + return;
> if (cpu_present(cpu))
> xen_arch_unregister_cpu(cpu);
Could you merge the two if conditions?
if (!cpu_online(cpu) && cpu_present(cpu))
xen_arch_unregister_cpu(cpu);
And while not really important, as we are called in the xenstore watch
thread only, it might be a good idea to move the first cpu_online()
test into the lock, i.e.:
lock_device_hotplug();
if (cpu_online(cpu))
device_offline(get_cpu_device(cpu));
unlock_device_hotplug();
This will make the code robust against reentry.
Juergen
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 7:48 ` Juergen Gross
@ 2018-09-07 9:24 ` Olaf Hering
2018-09-07 9:24 ` Olaf Hering
1 sibling, 0 replies; 18+ messages in thread
From: Olaf Hering @ 2018-09-07 9:24 UTC (permalink / raw)
To: Juergen Gross; +Cc: xen-devel, Boris Ostrovsky, open list
[-- Attachment #1.1: Type: text/plain, Size: 493 bytes --]
Am Fri, 7 Sep 2018 09:48:28 +0200
schrieb Juergen Gross <jgross@suse.com>:
> On 07/09/18 08:30, Olaf Hering wrote:
> > + if (cpu_online(cpu))
> > + return;
> > if (cpu_present(cpu))
> > xen_arch_unregister_cpu(cpu);
> Could you merge the two if conditions?
> if (!cpu_online(cpu) && cpu_present(cpu))
> xen_arch_unregister_cpu(cpu);
Is that any different, beside being wrong, from what the patch actually does?
It would still clear the present bit later on.
Olaf
[-- Attachment #1.2: Digitale Signatur von OpenPGP --]
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_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 7:48 ` Juergen Gross
2018-09-07 9:24 ` Olaf Hering
@ 2018-09-07 9:24 ` Olaf Hering
2018-09-07 9:50 ` Juergen Gross
2018-09-07 9:50 ` Juergen Gross
1 sibling, 2 replies; 18+ messages in thread
From: Olaf Hering @ 2018-09-07 9:24 UTC (permalink / raw)
To: Juergen Gross; +Cc: xen-devel, Boris Ostrovsky, open list
[-- Attachment #1: Type: text/plain, Size: 493 bytes --]
Am Fri, 7 Sep 2018 09:48:28 +0200
schrieb Juergen Gross <jgross@suse.com>:
> On 07/09/18 08:30, Olaf Hering wrote:
> > + if (cpu_online(cpu))
> > + return;
> > if (cpu_present(cpu))
> > xen_arch_unregister_cpu(cpu);
> Could you merge the two if conditions?
> if (!cpu_online(cpu) && cpu_present(cpu))
> xen_arch_unregister_cpu(cpu);
Is that any different, beside being wrong, from what the patch actually does?
It would still clear the present bit later on.
Olaf
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 9:24 ` Olaf Hering
@ 2018-09-07 9:50 ` Juergen Gross
2018-09-07 9:50 ` Juergen Gross
1 sibling, 0 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-07 9:50 UTC (permalink / raw)
To: Olaf Hering; +Cc: xen-devel, Boris Ostrovsky, open list
On 07/09/18 11:24, Olaf Hering wrote:
> Am Fri, 7 Sep 2018 09:48:28 +0200
> schrieb Juergen Gross <jgross@suse.com>:
>
>> On 07/09/18 08:30, Olaf Hering wrote:
>>> + if (cpu_online(cpu))
>>> + return;
>>> if (cpu_present(cpu))
>>> xen_arch_unregister_cpu(cpu);
>
>> Could you merge the two if conditions?
>> if (!cpu_online(cpu) && cpu_present(cpu))
>> xen_arch_unregister_cpu(cpu);
>
> Is that any different, beside being wrong, from what the patch actually does?
No. Just a matter of style.
> It would still clear the present bit later on.
This should be part of the if clause, of course.
Juergen
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 9:24 ` Olaf Hering
2018-09-07 9:50 ` Juergen Gross
@ 2018-09-07 9:50 ` Juergen Gross
1 sibling, 0 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-07 9:50 UTC (permalink / raw)
To: Olaf Hering; +Cc: xen-devel, Boris Ostrovsky, open list
On 07/09/18 11:24, Olaf Hering wrote:
> Am Fri, 7 Sep 2018 09:48:28 +0200
> schrieb Juergen Gross <jgross@suse.com>:
>
>> On 07/09/18 08:30, Olaf Hering wrote:
>>> + if (cpu_online(cpu))
>>> + return;
>>> if (cpu_present(cpu))
>>> xen_arch_unregister_cpu(cpu);
>
>> Could you merge the two if conditions?
>> if (!cpu_online(cpu) && cpu_present(cpu))
>> xen_arch_unregister_cpu(cpu);
>
> Is that any different, beside being wrong, from what the patch actually does?
No. Just a matter of style.
> It would still clear the present bit later on.
This should be part of the if clause, of course.
Juergen
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 6:30 [PATCH v3] xen: avoid crash in disable_hotplug_cpu Olaf Hering
2018-09-07 7:48 ` Juergen Gross
@ 2018-09-07 7:48 ` Juergen Gross
2018-09-07 13:33 ` Boris Ostrovsky
` (3 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-07 7:48 UTC (permalink / raw)
To: Olaf Hering, xen-devel; +Cc: Boris Ostrovsky, open list
On 07/09/18 08:30, Olaf Hering wrote:
> The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
> RIP: e030:device_offline+0x9/0xb0
> Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
> RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
> R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
> R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
> FS: 00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
> Call Trace:
> handle_vcpu_hotplug_event+0xb5/0xc0
> xenwatch_thread+0x80/0x140
> ? wait_woken+0x80/0x80
> kthread+0x112/0x130
> ? kthread_create_worker_on_cpu+0x40/0x40
> ret_from_fork+0x3a/0x50
>
> This happens because handle_vcpu_hotplug_event is called twice. In the
> first iteration cpu_present is still true, in the second iteration
> cpu_present is false which causes get_cpu_device to return NULL.
> In case of cpu#0, cpu_online is apparently always true.
>
> Fix this crash by checking if the cpu can be hotplugged, which is false
> for a cpu that was just removed.
>
> Also check if the cpu was actually offlined by device_remove, otherwise
> leave the cpu_present state as it is.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> ---
> drivers/xen/cpu_hotplug.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
> index d4265c8ebb22..68f9f663da08 100644
> --- a/drivers/xen/cpu_hotplug.c
> +++ b/drivers/xen/cpu_hotplug.c
> @@ -19,11 +19,15 @@ static void enable_hotplug_cpu(int cpu)
>
> static void disable_hotplug_cpu(int cpu)
> {
> + if (!cpu_is_hotpluggable(cpu))
> + return;
> if (cpu_online(cpu)) {
> lock_device_hotplug();
> device_offline(get_cpu_device(cpu));
> unlock_device_hotplug();
> }
> + if (cpu_online(cpu))
> + return;
> if (cpu_present(cpu))
> xen_arch_unregister_cpu(cpu);
Could you merge the two if conditions?
if (!cpu_online(cpu) && cpu_present(cpu))
xen_arch_unregister_cpu(cpu);
And while not really important, as we are called in the xenstore watch
thread only, it might be a good idea to move the first cpu_online()
test into the lock, i.e.:
lock_device_hotplug();
if (cpu_online(cpu))
device_offline(get_cpu_device(cpu));
unlock_device_hotplug();
This will make the code robust against reentry.
Juergen
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 6:30 [PATCH v3] xen: avoid crash in disable_hotplug_cpu Olaf Hering
2018-09-07 7:48 ` Juergen Gross
2018-09-07 7:48 ` Juergen Gross
@ 2018-09-07 13:33 ` Boris Ostrovsky
2018-09-07 13:33 ` Boris Ostrovsky
` (2 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: Boris Ostrovsky @ 2018-09-07 13:33 UTC (permalink / raw)
To: Olaf Hering, xen-devel; +Cc: Juergen Gross, open list
On 09/07/2018 02:30 AM, Olaf Hering wrote:
> The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
> RIP: e030:device_offline+0x9/0xb0
> Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
> RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
> R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
> R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
> FS: 00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
> Call Trace:
> handle_vcpu_hotplug_event+0xb5/0xc0
> xenwatch_thread+0x80/0x140
> ? wait_woken+0x80/0x80
> kthread+0x112/0x130
> ? kthread_create_worker_on_cpu+0x40/0x40
> ret_from_fork+0x3a/0x50
>
> This happens because handle_vcpu_hotplug_event is called twice. In the
> first iteration cpu_present is still true, in the second iteration
> cpu_present is false which causes get_cpu_device to return NULL.
> In case of cpu#0, cpu_online is apparently always true.
>
> Fix this crash by checking if the cpu can be hotplugged, which is false
> for a cpu that was just removed.
>
> Also check if the cpu was actually offlined by device_remove, otherwise
> leave the cpu_present state as it is.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> ---
> drivers/xen/cpu_hotplug.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
> index d4265c8ebb22..68f9f663da08 100644
> --- a/drivers/xen/cpu_hotplug.c
> +++ b/drivers/xen/cpu_hotplug.c
> @@ -19,11 +19,15 @@ static void enable_hotplug_cpu(int cpu)
>
> static void disable_hotplug_cpu(int cpu)
> {
> + if (!cpu_is_hotpluggable(cpu))
> + return;
> if (cpu_online(cpu)) {
> lock_device_hotplug();
> device_offline(get_cpu_device(cpu));
> unlock_device_hotplug();
> }
> + if (cpu_online(cpu))
> + return;
> if (cpu_present(cpu))
> xen_arch_unregister_cpu(cpu);
>
You don't get a warning in xen_init_lock_cpu() for CPU0?
Also, as a side question --- what is the purpose of 'xl vcpu-set <domid> 0'?
-boris
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 6:30 [PATCH v3] xen: avoid crash in disable_hotplug_cpu Olaf Hering
` (2 preceding siblings ...)
2018-09-07 13:33 ` Boris Ostrovsky
@ 2018-09-07 13:33 ` Boris Ostrovsky
2018-09-07 13:39 ` Olaf Hering
2018-09-07 13:39 ` Olaf Hering
2018-09-11 11:25 ` Juergen Gross
2018-09-11 11:25 ` Juergen Gross
5 siblings, 2 replies; 18+ messages in thread
From: Boris Ostrovsky @ 2018-09-07 13:33 UTC (permalink / raw)
To: Olaf Hering, xen-devel; +Cc: Juergen Gross, open list
On 09/07/2018 02:30 AM, Olaf Hering wrote:
> The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
> RIP: e030:device_offline+0x9/0xb0
> Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
> RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
> R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
> R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
> FS: 00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
> Call Trace:
> handle_vcpu_hotplug_event+0xb5/0xc0
> xenwatch_thread+0x80/0x140
> ? wait_woken+0x80/0x80
> kthread+0x112/0x130
> ? kthread_create_worker_on_cpu+0x40/0x40
> ret_from_fork+0x3a/0x50
>
> This happens because handle_vcpu_hotplug_event is called twice. In the
> first iteration cpu_present is still true, in the second iteration
> cpu_present is false which causes get_cpu_device to return NULL.
> In case of cpu#0, cpu_online is apparently always true.
>
> Fix this crash by checking if the cpu can be hotplugged, which is false
> for a cpu that was just removed.
>
> Also check if the cpu was actually offlined by device_remove, otherwise
> leave the cpu_present state as it is.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> ---
> drivers/xen/cpu_hotplug.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
> index d4265c8ebb22..68f9f663da08 100644
> --- a/drivers/xen/cpu_hotplug.c
> +++ b/drivers/xen/cpu_hotplug.c
> @@ -19,11 +19,15 @@ static void enable_hotplug_cpu(int cpu)
>
> static void disable_hotplug_cpu(int cpu)
> {
> + if (!cpu_is_hotpluggable(cpu))
> + return;
> if (cpu_online(cpu)) {
> lock_device_hotplug();
> device_offline(get_cpu_device(cpu));
> unlock_device_hotplug();
> }
> + if (cpu_online(cpu))
> + return;
> if (cpu_present(cpu))
> xen_arch_unregister_cpu(cpu);
>
You don't get a warning in xen_init_lock_cpu() for CPU0?
Also, as a side question --- what is the purpose of 'xl vcpu-set <domid> 0'?
-boris
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 13:33 ` Boris Ostrovsky
@ 2018-09-07 13:39 ` Olaf Hering
2018-09-07 13:39 ` Olaf Hering
1 sibling, 0 replies; 18+ messages in thread
From: Olaf Hering @ 2018-09-07 13:39 UTC (permalink / raw)
To: Boris Ostrovsky; +Cc: Juergen Gross, xen-devel, open list
[-- Attachment #1.1: Type: text/plain, Size: 236 bytes --]
Am Fri, 7 Sep 2018 09:33:20 -0400
schrieb Boris Ostrovsky <boris.ostrovsky@oracle.com>:
> what is the purpose of 'xl vcpu-set <domid> 0'?
Likely just a script that went wrong. But that command should not break the dom0.
Olaf
[-- Attachment #1.2: Digitale Signatur von OpenPGP --]
[-- Type: application/pgp-signature, Size: 195 bytes --]
[-- Attachment #2: Type: text/plain, Size: 157 bytes --]
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 13:33 ` Boris Ostrovsky
2018-09-07 13:39 ` Olaf Hering
@ 2018-09-07 13:39 ` Olaf Hering
1 sibling, 0 replies; 18+ messages in thread
From: Olaf Hering @ 2018-09-07 13:39 UTC (permalink / raw)
To: Boris Ostrovsky; +Cc: xen-devel, Juergen Gross, open list
[-- Attachment #1: Type: text/plain, Size: 236 bytes --]
Am Fri, 7 Sep 2018 09:33:20 -0400
schrieb Boris Ostrovsky <boris.ostrovsky@oracle.com>:
> what is the purpose of 'xl vcpu-set <domid> 0'?
Likely just a script that went wrong. But that command should not break the dom0.
Olaf
[-- Attachment #2: Digitale Signatur von OpenPGP --]
[-- Type: application/pgp-signature, Size: 195 bytes --]
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 6:30 [PATCH v3] xen: avoid crash in disable_hotplug_cpu Olaf Hering
` (3 preceding siblings ...)
2018-09-07 13:33 ` Boris Ostrovsky
@ 2018-09-11 11:25 ` Juergen Gross
2018-09-11 14:29 ` Boris Ostrovsky
2018-09-11 14:29 ` Boris Ostrovsky
2018-09-11 11:25 ` Juergen Gross
5 siblings, 2 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-11 11:25 UTC (permalink / raw)
To: Olaf Hering, xen-devel; +Cc: Boris Ostrovsky, open list
On 07/09/18 08:30, Olaf Hering wrote:
> The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
> RIP: e030:device_offline+0x9/0xb0
> Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
> RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
> R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
> R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
> FS: 00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
> Call Trace:
> handle_vcpu_hotplug_event+0xb5/0xc0
> xenwatch_thread+0x80/0x140
> ? wait_woken+0x80/0x80
> kthread+0x112/0x130
> ? kthread_create_worker_on_cpu+0x40/0x40
> ret_from_fork+0x3a/0x50
>
> This happens because handle_vcpu_hotplug_event is called twice. In the
> first iteration cpu_present is still true, in the second iteration
> cpu_present is false which causes get_cpu_device to return NULL.
> In case of cpu#0, cpu_online is apparently always true.
>
> Fix this crash by checking if the cpu can be hotplugged, which is false
> for a cpu that was just removed.
>
> Also check if the cpu was actually offlined by device_remove, otherwise
> leave the cpu_present state as it is.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-11 11:25 ` Juergen Gross
@ 2018-09-11 14:29 ` Boris Ostrovsky
2018-09-11 14:29 ` Boris Ostrovsky
1 sibling, 0 replies; 18+ messages in thread
From: Boris Ostrovsky @ 2018-09-11 14:29 UTC (permalink / raw)
To: Juergen Gross, Olaf Hering, xen-devel; +Cc: open list
On 9/11/18 7:25 AM, Juergen Gross wrote:
>
> Reviewed-by: Juergen Gross <jgross@suse.com>
So is it v3 or v4, you gave R-b for both. (I slightly prefer v3, but
either is fine).
-boris
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Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-11 11:25 ` Juergen Gross
2018-09-11 14:29 ` Boris Ostrovsky
@ 2018-09-11 14:29 ` Boris Ostrovsky
2018-09-11 14:29 ` Juergen Gross
2018-09-11 14:29 ` Juergen Gross
1 sibling, 2 replies; 18+ messages in thread
From: Boris Ostrovsky @ 2018-09-11 14:29 UTC (permalink / raw)
To: Juergen Gross, Olaf Hering, xen-devel; +Cc: open list
On 9/11/18 7:25 AM, Juergen Gross wrote:
>
> Reviewed-by: Juergen Gross <jgross@suse.com>
So is it v3 or v4, you gave R-b for both. (I slightly prefer v3, but
either is fine).
-boris
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-11 14:29 ` Boris Ostrovsky
@ 2018-09-11 14:29 ` Juergen Gross
2018-09-11 14:29 ` Juergen Gross
1 sibling, 0 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-11 14:29 UTC (permalink / raw)
To: Boris Ostrovsky, Olaf Hering, xen-devel; +Cc: open list
On 11/09/18 16:29, Boris Ostrovsky wrote:
> On 9/11/18 7:25 AM, Juergen Gross wrote:
>>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
>
> So is it v3 or v4, you gave R-b for both. (I slightly prefer v3, but
> either is fine).
V4 is better as it does the online test only after acquiring the
hotplug lock.
Juergen
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-11 14:29 ` Boris Ostrovsky
2018-09-11 14:29 ` Juergen Gross
@ 2018-09-11 14:29 ` Juergen Gross
1 sibling, 0 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-11 14:29 UTC (permalink / raw)
To: Boris Ostrovsky, Olaf Hering, xen-devel; +Cc: open list
On 11/09/18 16:29, Boris Ostrovsky wrote:
> On 9/11/18 7:25 AM, Juergen Gross wrote:
>>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
>
> So is it v3 or v4, you gave R-b for both. (I slightly prefer v3, but
> either is fine).
V4 is better as it does the online test only after acquiring the
hotplug lock.
Juergen
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] xen: avoid crash in disable_hotplug_cpu
2018-09-07 6:30 [PATCH v3] xen: avoid crash in disable_hotplug_cpu Olaf Hering
` (4 preceding siblings ...)
2018-09-11 11:25 ` Juergen Gross
@ 2018-09-11 11:25 ` Juergen Gross
5 siblings, 0 replies; 18+ messages in thread
From: Juergen Gross @ 2018-09-11 11:25 UTC (permalink / raw)
To: Olaf Hering, xen-devel; +Cc: Boris Ostrovsky, open list
On 07/09/18 08:30, Olaf Hering wrote:
> The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
> RIP: e030:device_offline+0x9/0xb0
> Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
> RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
> R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
> R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
> FS: 00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
> Call Trace:
> handle_vcpu_hotplug_event+0xb5/0xc0
> xenwatch_thread+0x80/0x140
> ? wait_woken+0x80/0x80
> kthread+0x112/0x130
> ? kthread_create_worker_on_cpu+0x40/0x40
> ret_from_fork+0x3a/0x50
>
> This happens because handle_vcpu_hotplug_event is called twice. In the
> first iteration cpu_present is still true, in the second iteration
> cpu_present is false which causes get_cpu_device to return NULL.
> In case of cpu#0, cpu_online is apparently always true.
>
> Fix this crash by checking if the cpu can be hotplugged, which is false
> for a cpu that was just removed.
>
> Also check if the cpu was actually offlined by device_remove, otherwise
> leave the cpu_present state as it is.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 18+ messages in thread