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

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Monday, December 30, 2013 03:58:43 PM Kashyap Chamarthy wrote:
> On 12/29/2013 04:04 PM, Rafael J. Wysocki wrote:
> > On Sunday, December 29, 2013 01:12:18 PM Kashyap Chamarthy wrote:
> >> [. . .]
> >>
> >>>> Here's host dmesg: https://bugzilla.kernel.org/attachment.cgi?id=119751
> >>>>
> >>>>>> Can you ftrace the failure?
> >>>>
> >>>> Can try, need some time (rest of the day I'll be away travelling,
> >>>> will try to do it over the weekend, and update the Kernel
> >>>> bugzilla with observations).
> >>>>
> >>>>>>
> >>>>> Ugh, it looks like guest dmesg but there are KVM messages there too ("[
> >>>>> 281.443662] kvm [2452]: vcpu0 unhandled rdmsr: 0xe8" is unhandled access
> >>>>> to MSR_IA32_APERF I was talking about above), so I guess this is nested
> >>>>> guest invocation? 
> >>>>
> >>>> Yeah -- sorry, I forgot to note it's in a nested environment :(
> >>>>
> >>>>> Does it happen in non nested guest?
> >>>>
> >>>> I need to that.
> >>>>
> >>>> Note to self: Also try with a newer Kernel on the host.
> >>>
> >>> Please try the patch I posted earlier today when you're at it:
> >>>
> >>> https://patchwork.kernel.org/patch/3411991/
> >>
> >> I applied the patch & tried to build the Kernel, it failed with:
> >>
> >> =======
> >> .
> >> .
> >> .
> >> Generating a 4096 bit RSA private key
> >> ............................................................................................................drivers/cpufreq/intel_pstate.c:
> >> In function 'intel_pstate_init_cpu':
> >> drivers/cpufreq/intel_pstate.c:617:18: error: 'struct pstate_data' has no member named
> >> 'current_state'
> >>   if (!cpu->pstate.current_state) {
> > 
> > My bad, that should have been current_pstate.  Updated patch is appended.
> > 
> > Thanks,
> > Rafael
> > 
> > 
> > ---
> >  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;