Re: [PATCH v4 1/2] x86, tsc: Fallback to normal calibration if fastMSR calibration fails

From: Thomas Gleixner
Date: Mon Feb 10 2014 - 05:32:27 EST


On Mon, 10 Feb 2014, Mika Westerberg wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>
> If we cannot calibrate TSC via MSR based calibration
> try_msr_calibrate_tsc() stores zero to fast_calibrate and returns that to
> the caller. This value gets then propagated further to clockevents code
> resulting division by zero oops like the one below:
>
> divide error: 0000 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 3.13.0+ #47
> task: ffff880075508000 ti: ffff880075506000 task.ti: ffff880075506000
> RIP: 0010:[<ffffffff810aec14>] [<ffffffff810aec14>] clockevents_config.part.3+0x24/0xa0
> RSP: 0000:ffff880075507e58 EFLAGS: 00010246
> RAX: ffffffffffffffff RBX: ffff880079c0cd80 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff
> RBP: ffff880075507e70 R08: 0000000000000001 R09: 00000000000000be
> R10: 00000000000000bd R11: 0000000000000003 R12: 000000000000b008
> R13: 0000000000000008 R14: 000000000000b010 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff880079c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: ffff880079fff000 CR3: 0000000001c0b000 CR4: 00000000001006f0
> Stack:
> ffff880079c0cd80 000000000000b008 0000000000000008 ffff880075507e88
> ffffffff810aecb0 ffff880079c0cd80 ffff880075507e98 ffffffff81030168
> ffff880075507ed8 ffffffff81d1104f 00000000000000c3 0000000000000000
> Call Trace:
> [<ffffffff810aecb0>] clockevents_config_and_register+0x20/0x30
> [<ffffffff81030168>] setup_APIC_timer+0xc8/0xd0
> [<ffffffff81d1104f>] setup_boot_APIC_clock+0x4cc/0x4d8
> [<ffffffff81d0f5de>] native_smp_prepare_cpus+0x3dd/0x3f0
> [<ffffffff81d02ee9>] kernel_init_freeable+0xc3/0x205
> [<ffffffff8177c910>] ? rest_init+0x90/0x90
> [<ffffffff8177c91e>] kernel_init+0xe/0x120
> [<ffffffff8178deec>] ret_from_fork+0x7c/0xb0
> [<ffffffff8177c910>] ? rest_init+0x90/0x90
>
> Prevent this from happening by:
> 1) Modifying try_msr_calibrate_tsc() to return calibration value or zero
> if it fails.
> 2) Check this return value in native_calibrate_tsc() and in case of zero
> fallback to use normal non-MSR based calibration.
>
> Reported-and-tested-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
> Thomas, I hope you don't mind that I added your SoB to the patch. It is
> after all from you.

You just missed to add your own SOB which tells us that you conveyed
the patch.

Thanks,

tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/