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@xxxxxxxxx> 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@xxxxxxxxxx> Cc: Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> --- 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;
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