linux-kernel - Re: i8k_smm_func() takes enormous of time to execute

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Date:   Mon, 4 Dec 2017 11:35:07 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Oleksandr Natalenko <oleksandr@...alenko.name>
Cc:     Jean Delvare <jdelvare@...e.de>,
        Jonathan Buzzard <jonathan@...zard.org.uk>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mario Limonciello <mario.limonciello@...l.com>
Subject: Re: i8k_smm_func() takes enormous of time to execute

On Friday 24 November 2017 13:28:59 Oleksandr Natalenko wrote:
> On pátek 24. listopadu 2017 12:25:43 CET Pali Rohár wrote:
> > On Friday 24 November 2017 12:17:30 Oleksandr Natalenko wrote:
> > > > There are two patches waiting to be tested in
> > > > https://bugzilla.kernel.org/show_bug.cgi?id=195751
> > > 
> > > Tested and attached a couple of patches on top of those to the BZ. If
> > > disabling fan control is the only approach here, I can confirm that this
> > > works.
> > 
> > Hi! Please figure out which SMM call (they are identified by eax and ebx
> > registers) cause this freeze. So we would now what needs to be
> > blacklisted.
> 
> Here it goes:
> 
> [ 7.191081] dell_smm_hwmon: smm(0x10a3 0x0000) = 0x002e (took     1837 usecs)
> [ 7.194007] dell_smm_hwmon: smm(0x00a3 0x0001) = 0xffff (took      151 usecs)
> [ 7.198239] dell_smm_hwmon: smm(0x00a3 0x0000) = 0x0002 (took     1411 usecs)
> [ 7.199095] dell_smm_hwmon: smm(0x02a3 0x0001) = 0xffff (took       71 usecs)
> [ 7.700493] dell_smm_hwmon: smm(0x02a3 0x0000) = 0x157c (took   488912 usecs)
> [ 7.701277] dell_smm_hwmon: smm(0x0025 0X0000) = 0xffff (took       71 usecs)
> 
> 0x02a3 is I8K_SMM_GET_SPEED.

Ok, so it is really a good idea to disable fan control completely on your machine.

Your last patch in bugzilla looks ok, you add my Reviewed-by: Pali Rohár <pali.rohar@...il.com>

-- 
Pali Rohár
pali.rohar@...il.com