Re: intel_pstate divide error with v3.13-rc4-256-gb7000ad

[Dirk Brandewie <dirk.brandewie@gmail.com>]

Hi All,

Sorry for being late to the party but I just got back from vacation.

There is something deeply wrong here.  We should have never gotten to
intel_pstate_init_cpu().  The VM had to have returned value from the read
of the max pstate at driver init time and 0 when the CPU was being brought up.

intel_pstate_msrs_not_valid() was added to solve this issue early on
if I remember correctly it was Josh that reported it then.  Is there
a definative way to detect whether we are running in a VM?

Can some one tell me how the nested environment differs in regards to
reading MSRs?

TIA
--Dirk

On 12/30/2013 06:07 PM, Rafael J. Wysocki wrote:
>>> ---
>>>   drivers/cpufreq/intel_pstate.c |    5 +++++
>>>   1 file changed, 5 insertions(+)
>>>
>>> Index: linux-pm/drivers/cpufreq/intel_pstate.c
>>> ===================================================================
>>> --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
>>> +++ linux-pm/drivers/cpufreq/intel_pstate.c
>>> @@ -614,6 +614,11 @@ static int intel_pstate_init_cpu(unsigne
>>>   	cpu = all_cpu_data[cpunum];
>>>
>>>   	intel_pstate_get_cpu_pstates(cpu);
>>> +	if (!cpu->pstate.current_pstate) {
>>> +		all_cpu_data[cpunum] = NULL;
>>> +		kfree(cpu);
>>> +		return -ENODATA;
>>> +	}
>>>
>>>   	cpu->cpu = cpunum;
>>>
>>>
>>
>>
>> Thanks Rafel, I can confirm this patch helps.
>
> Awesome, thanks!
>
> Below is an official version with a changelog.  I'll queue it up as a fix
> for 3.13.
>
> Thanks,
> Rafael
>
>
> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Subject: intel_pstate: Fail initialization if P-state information is missing
>
> If pstate.current_pstate is 0 after the initial
> intel_pstate_get_cpu_pstates(), this means that we were unable to
> obtain any useful P-state information and there is no reason to
> continue, so free memory and return an error in that case.
>
> This fixes the following divide error occuring in a nested KVM
> guest:
>
> Intel P-state driver initializing.
> Intel pstate controlling: cpu 0
> cpufreq: __cpufreq_add_dev: ->get() failed
> divide error: 0000 [#1] SMP
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-0.rc4.git5.1.fc21.x86_64 #1
> Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> task: ffff88001ea20000 ti: ffff88001e9bc000 task.ti: ffff88001e9bc000
> RIP: 0010:[<ffffffff815c551d>]  [<ffffffff815c551d>] intel_pstate_timer_func+0x11d/0x2b0
> RSP: 0000:ffff88001ee03e18  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff88001a454348 RCX: 0000000000006100
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff88001ee03e38 R08: 0000000000000000 R09: 0000000000000000
> R10: ffff88001ea20000 R11: 0000000000000000 R12: 00000c0a1ea20000
> R13: 1ea200001ea20000 R14: ffffffff815c5400 R15: ffff88001a454348
> FS:  0000000000000000(0000) GS:ffff88001ee00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 0000000000000000 CR3: 0000000001c0c000 CR4: 00000000000006f0
> Stack:
>   fffffffb1a454390 ffffffff821a4500 ffff88001a454390 0000000000000100
>   ffff88001ee03ea8 ffffffff81083e9a ffffffff81083e15 ffffffff82d5ed40
>   ffffffff8258cc60 0000000000000000 ffffffff81ac39de 0000000000000000
> Call Trace:
>   <IRQ>
>   [<ffffffff81083e9a>] call_timer_fn+0x8a/0x310
>   [<ffffffff81083e15>] ? call_timer_fn+0x5/0x310
>   [<ffffffff815c5400>] ? pid_param_set+0x130/0x130
>   [<ffffffff81084354>] run_timer_softirq+0x234/0x380
>   [<ffffffff8107aee4>] __do_softirq+0x104/0x430
>   [<ffffffff8107b5fd>] irq_exit+0xcd/0xe0
>   [<ffffffff81770645>] smp_apic_timer_interrupt+0x45/0x60
>   [<ffffffff8176efb2>] apic_timer_interrupt+0x72/0x80
>   <EOI>
>   [<ffffffff810e15cd>] ? vprintk_emit+0x1dd/0x5e0
>   [<ffffffff81757719>] printk+0x67/0x69
>   [<ffffffff815c1493>] __cpufreq_add_dev.isra.13+0x883/0x8d0
>   [<ffffffff815c14f0>] cpufreq_add_dev+0x10/0x20
>   [<ffffffff814a14d1>] subsys_interface_register+0xb1/0xf0
>   [<ffffffff815bf5cf>] cpufreq_register_driver+0x9f/0x210
>   [<ffffffff81fb19af>] intel_pstate_init+0x27d/0x3be
>   [<ffffffff81761e3e>] ? mutex_unlock+0xe/0x10
>   [<ffffffff81fb1732>] ? cpufreq_gov_dbs_init+0x12/0x12
>   [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
>   [<ffffffff8109dbf5>] ? parse_args+0x225/0x3f0
>   [<ffffffff81f64193>] kernel_init_freeable+0x1fc/0x287
>   [<ffffffff81f638d0>] ? do_early_param+0x88/0x88
>   [<ffffffff8174b530>] ? rest_init+0x150/0x150
>   [<ffffffff8174b53e>] kernel_init+0xe/0x130
>   [<ffffffff8176e27c>] ret_from_fork+0x7c/0xb0
>   [<ffffffff8174b530>] ? rest_init+0x150/0x150
> Code: c1 e0 05 48 63 bc 03 10 01 00 00 48 63 83 d0 00 00 00 48 63 d6 48 c1 e2 08 c1 e1 08 4c 63 c2 48 c1 e0 08 48 98 48 c1 e0 08 48 99 <49> f7 f8 48 98 48 0f af f8 48 c1 ff 08 29 f9 89 ca c1 fa 1f 89
> RIP  [<ffffffff815c551d>] intel_pstate_timer_func+0x11d/0x2b0
>   RSP <ffff88001ee03e18>
> ---[ end trace f166110ed22cc37a ]---
> Kernel panic - not syncing: Fatal exception in interrupt
>
> Reported-and-tested-by: Kashyap Chamarthy <kchamart@redhat.com>
> Cc: Josh Boyer <jwboyer@fedoraproject.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>   drivers/cpufreq/intel_pstate.c |    5 +++++
>   1 file changed, 5 insertions(+)
>
> Index: linux-pm/drivers/cpufreq/intel_pstate.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> +++ linux-pm/drivers/cpufreq/intel_pstate.c
> @@ -614,6 +614,11 @@ static int intel_pstate_init_cpu(unsigne
>   	cpu = all_cpu_data[cpunum];
>
>   	intel_pstate_get_cpu_pstates(cpu);
> +	if (!cpu->pstate.current_pstate) {
> +		all_cpu_data[cpunum] = NULL;
> +		kfree(cpu);
> +		return -ENODATA;
> +	}
>
>   	cpu->cpu = cpunum;
>
>