Re: [Help Test] kdump, x86, acpi: Reproduce CPU0 SMI corruption issue after unsetting BSP flag

Jingbai Ma
2013-08-13T10:56:05Z

On 08/06/2013 05:19 PM, HATAYAMA Daisuke wrote:
> Hello,
>
> I've addressing kdump restriction that there's only one cpu available
> on the kdump 2nd kernel. Now I need to check if the following CPU0 SMI
> corruption issue fixed in the following commit can again be reproduced
> by unsetting BSP flag of the boot cpu:
>
> commit 74b5820808215f65b70b05a099d6d3c969b82689
> Author: Bjorn Helgaas<bjorn.helgaas@hp.com>
> Date: Wed Jul 29 15:54:25 2009 -0600
>
> ACPI: bind workqueues to CPU 0 to avoid SMI corruption
>
> On some machines, a software-initiated SMI causes corruption unless the
> SMI runs on CPU 0. An SMI can be initiated by any AML, but typically it's
> done in GPE-related methods that are run via workqueues, so we can avoid
> the known corruption cases by binding the workqueues to CPU 0.
>
> References:
> http://bugzilla.kernel.org/show_bug.cgi?id=13751
> https://bugs.launchpad.net/bugs/157171
> https://bugs.launchpad.net/bugs/157691
>
> Signed-off-by: Bjorn Helgaas<bjorn.helgaas@hp.com>
> Signed-off-by: Len Brown<len.brown@intel.com>
>
> The reason is that in the current situation, I have two ideas to deal
> with the avove kdump restriction:
>
> 1) Disable BSP at the 2nd kernel, posted at:
> [PATCH v1 0/2] x86, apic: Disable BSP if boot cpu is AP
> https://lkml.org/lkml/2012/10/16/15
>
> 2) Unset BSP flag at the 1st kernel, suggested by Eric Biederman
> during the discussion of the idea 1).
>
> On the idea 1), BSP is disabled on the kdump 2nd kernel. My conclusion
> is that we have no method to reset BSP, i.e. recover BPS's healthy
> state, while we can recover AP by means of INIT as described in MP
> specification.
>
> The idea 2) is simpler. We unset BSP flag of the boot cpu at 1st
> kernel. The behaviour when receiving INIT depends on whether or not
> BSP flag is set or not on its MSR; we can set and unset BSP flag of
> MSR freely at runtime. (I don't mean we should).
>
> So, next thing I should do is to evalute risk of the idea 2). In fact,
> during the discussion of the idea 1), HPA pointed out that some kind
> of firmware affects if BSP flag is unset. Also, maybe from the same
> reason, recently introduced cpu0 hot-plugging feature by Fenghua Yu
> doesn't appear to unset BSP flag.
>
> The biggest problem next is that I don't have any machines reported in
> the bugzilla articles; this issue inherently depends on firmware.
>
> So, could anyone help testing the idea 2) above if you have which of
> the following machines? (or other ones that can lead to the same bug)
>
> - HP Compaq 6910p
> - HP Compaq 6710b
> - HP Compaq 6710s
> - HP Compaq 6510b
> - HP Compaq 2510p
>
> I prepared a small programs for this test. See the attached file.
> The steps to try to reproduce the bug is as follows:
>
> 1. $ tar xf bsp_flag_modules.tar.gz; cd bsp_flag_modules
> 2. $ make # to build these programs
> 3. $ insmod unsetbspflag.ko # to unset BSP flag of the boot cpu
> 4. $ insmod getcpuinfo.ko # to confirm if BSP flag of the boot cpu has
> # been unset.
> $ dmesg | tail
> 5. Close the lid of the machine.
> 6. Wait some minutes if necessary.
> 7. Open the lid and you can see oops on the screen if bug has
> successfully been reproduced.
>

I couldn't find any model list above, but found one HP EliteBook 6930p.
I tested this machine with kernel 2.6.30 first. After resuming from
suspend, system hang.

Then, I tested with kernel 3.11.0-rc5, it worked well, could resume from
suspend without any problem.

Next, I tested your program to clear BSP flag, I found the
unsetbspflag.ko didn't work everytime, sometimes I have to execute
insmod/rmmod several times to clear the BSP flag. (I used your
getcpuinfo.ko to check the BSP flag)

cpu: 0 bios_apic: 0 apic: 0 AP
cpu: 1 bios_apic: 1 apic: 1 AP

I suspended it, and them resumed it. This machine resumed from suspend
successfully, but the BSP flag has been set back:

cpu: 0 bios_apic: 0 apic: 0 BSP
cpu: 1 bios_apic: 1 apic: 1 AP

That's all my observation. Hope it's helpful.

--
Thanks,
Jingbai Ma