i8k_smm_func() takes enormous of time to execute

I've noticed that querying Dell Vostro 3360 hwmon sensor freezes the system completely (like, really completely, even mouse cursor does not move, and sound playback stops) for approx. half of a second. Then, system recovers and runs as usual. Also, sensor readings are okay, for instance:

===

$ sensors dell_smm-virtual-0
dell_smm-virtual-0
Adapter: Virtual device
Processor Fan: 5615 RPM
CPU:            +51.0°C  
Ambient:        +36.0°C  
Other:          +63.0°C  
SODIMM:         +41.0°C 
===

So, I've used trace-cmd to check what takes that much amount of time to execute, and got this:

===

# trace-cmd record -p function_graph -l i8k_smm -F sensors dell_smm-virtual-0
$ trace-cmd report
...
sensors-23694 [002] 89099.214369: funcgraph_entry:      # 503440.746 us |  
i8k_smm();
...
===

Clearly, 0.5 s delay.

Looking at i8k_smm(), it calls i8k_smm_func() on 0th CPU:

===
232 ret = smp_call_on_cpu(0, i8k_smm_func, regs, true);
===

which, in turn, does some asm magic.

I know that SMM is kinda "black box", and kernel has little to do with it, but I think that under Windows, for instance, it would work without freezes. So, likely, querying SMM might be done differently.

I do not know how to approach this issue, thus asking for help/advice. Also, CCing Jonathan since the comment before asm magic says this:

===
137 * Call the System Management Mode BIOS. Code provided by Jonathan
Buzzard.
===

This was also reported in various places before, for instance, [1], but unfortunately, without any solution.

Hi Oleksandr,

Quoted 52 lines · Oleksandr Natalenko

I've noticed that querying Dell Vostro 3360 hwmon sensor freezes the system
completely (like, really completely, even mouse cursor does not move, and sound playback stops) for approx. half of a second. Then, system recovers and runs as usual. Also, sensor readings are okay, for instance:

===

$ sensors dell_smm-virtual-0
dell_smm-virtual-0
Adapter: Virtual device
Processor Fan: 5615 RPM
CPU:            +51.0°C
Ambient:        +36.0°C
Other:          +63.0°C
SODIMM:         +41.0°C
===

So, I've used trace-cmd to check what takes that much amount of time to execute, and got this:

===

# trace-cmd record -p function_graph -l i8k_smm -F sensors
dell_smm-virtual-0 $ trace-cmd report
...
sensors-23694 [002] 89099.214369: funcgraph_entry:      # 503440.746 us |
i8k_smm();
...
===

Clearly, 0.5 s delay.

Looking at i8k_smm(), it calls i8k_smm_func() on 0th CPU:

===

232 ret = smp_call_on_cpu(0, i8k_smm_func, regs, true);

===

which, in turn, does some asm magic.

I know that SMM is kinda "black box", and kernel has little to do with it, but I think that under Windows, for instance, it would work without freezes. So, likely, querying SMM might be done differently.

I do not know how to approach this issue, thus asking for help/advice. Also, CCing Jonathan since the comment before asm magic says this:

===

137 * Call the System Management Mode BIOS. Code provided by Jonathan

Quoted 5 lines

Buzzard.
===

This was also reported in various places before, for instance, [1], but unfortunately, without any solution.

There are two patches waiting to be tested in
https://bugzilla.kernel.org/show_bug.cgi?id=195751

Quoted 2 lines

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.

Quoted 6 lines · On Friday 24 November 2017 12:17:30 Oleksandr Natalenko wrote:

Quoted 2 lines

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.

Quoted 11 lines · On pátek 24. listopadu 2017 12:25:43 CET Pali Rohár wrote:

Quoted 6 lines · On Friday 24 November 2017 12:17:30 Oleksandr Natalenko wrote:

Quoted 2 lines

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.

Quoted 22 lines · On Friday 24 November 2017 13:28:59 Oleksandr Natalenko wrote:

Quoted 11 lines · On pátek 24. listopadu 2017 12:25:43 CET Pali Rohár wrote:

Quoted 6 lines · On Friday 24 November 2017 12:17:30 Oleksandr Natalenko wrote:

Quoted 2 lines

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)

Quoted 1 line

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 <[email protected]>

Hi.

Quoted 29 lines · Pali Rohár

Quoted 28 lines · On Friday 24 November 2017 13:28:59 Oleksandr Natalenko wrote:

Quoted 11 lines · On pátek 24. listopadu 2017 12:25:43 CET Pali Rohár wrote:

Quoted 6 lines · On Friday 24 November 2017 12:17:30 Oleksandr Natalenko wrote:

Quoted 2 lines

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)

Quoted 4 lines

Quoted 1 line

0x02a3 is I8K_SMM_GET_SPEED.

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

This still doesn't explain why things work in non-Linux environment…

But as a workaround, okay, let it be.

Quoted 2 lines

Your last patch in bugzilla looks ok, you add my Reviewed-by: Pali Rohár <[email protected]>

Could you please advice on how to proceed further? I can submit all 3 patches (incl. yours two), to a ML.

Quoted 5 lines

Quoted 2 lines

Your last patch in bugzilla looks ok, you add my Reviewed-by: Pali Rohár <[email protected]>

Could you please advice on how to proceed further? I can submit all 3 patches (incl. yours two), to a ML.

Now it is up to hwmon maintainers (Jean Delvare & Guenter Roeck) to pick up these patches. I think nothing more is needed from your side. (And if yes, Jean would write.)

Quoted 10 lines · On Monday 04 December 2017 13:18:29 Pali Rohár wrote:

Quoted 5 lines

Quoted 2 lines

Your last patch in bugzilla looks ok, you add my Reviewed-by: Pali Rohár <[email protected]>

Could you please advice on how to proceed further? I can submit all 3 patches (incl. yours two), to a ML.

Now it is up to hwmon maintainers (Jean Delvare & Guenter Roeck) to pick up these patches. I think nothing more is needed from your side. (And if yes, Jean would write.)

Jean Delvare & Guenter Roeck: PING

Can you process patches from that bugzilla ticket?
https://bugzilla.kernel.org/show_bug.cgi?id=195751

Hi, Jonathan, Mario et al.

I've noticed that querying Dell Vostro 3360 hwmon sensor freezes the system completely (like, really completely, even mouse cursor does not move, and sound playback stops) for approx. half of a second. Then, system recovers and runs as usual. Also, sensor readings are okay, for instance:

===

$ sensors dell_smm-virtual-0
dell_smm-virtual-0
Adapter: Virtual device
Processor Fan: 5615 RPM
CPU:            +51.0°C  
Ambient:        +36.0°C  
Other:          +63.0°C  
SODIMM:         +41.0°C 
===

So, I've used trace-cmd to check what takes that much amount of time to execute, and got this:

===

# trace-cmd record -p function_graph -l i8k_smm -F sensors dell_smm-virtual-0
$ trace-cmd report
...
sensors-23694 [002] 89099.214369: funcgraph_entry:      # 503440.746 us |  
i8k_smm();
...
===

Clearly, 0.5 s delay.

Looking at i8k_smm(), it calls i8k_smm_func() on 0th CPU:

===
232 ret = smp_call_on_cpu(0, i8k_smm_func, regs, true);
===

which, in turn, does some asm magic.

I know that SMM is kinda "black box", and kernel has little to do with it, but I think that under Windows, for instance, it would work without freezes. So, likely, querying SMM might be done differently.

I do not know how to approach this issue, thus asking for help/advice. Also, CCing Jonathan since the comment before asm magic says this:

===
137 * Call the System Management Mode BIOS. Code provided by Jonathan
Buzzard.
===

This was also reported in various places before, for instance, [1], but unfortunately, without any solution.

Thanks.

Regards,
Oleksandr

[1] https://bugs.launchpad.net/ubuntu/+source/acpi/+bug/10490