Re: [PATCH 2/2] x86, microcode: Ensure that module is only loaded for

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

On 04/17/2012 08:20 PM, Borislav Petkov wrote:

> On Tue, Apr 17, 2012 at 07:41:22PM +0530, Srivatsa S. Bhat wrote:
>> On 04/16/2012 07:13 PM, Borislav Petkov wrote:
>>
>>> On Mon, Apr 16, 2012 at 02:12:00PM +0530, Srivatsa S. Bhat wrote:
>>>> I guess a similar change in intel microcode driver would also be
>>>> worthwhile, right? If so, then the below patch might be useful:
>>>
>>> AFAICT, you'd need to test this on a box which is not supported (family
>>> check below). Or you can tweak the family check so that it doesn't
>>> apply and run it on a test box of yours to see whether the module still
>>> unloads properly in the error case (and doesn't remain loaded as in
>>> our case due to something in sysfs remaining registered although it
>>> shouldn't).
>>>
>> Judging by the nature of the code itself, its evident that this problem
>> is not restricted to AMD alone. In any case, I went ahead and did the
>> (tweaked) test that you suggested and here is the result:
>>
>> 1. dmesg logs :
>> [   21.912451] microcode: CPU0 not a capable Intel processor
>> [   21.916028] microcode: CPU1 not a capable Intel processor
>> [   21.934624] microcode: CPU2 not a capable Intel processor
>> [   21.940276] microcode: CPU3 not a capable Intel processor
>> [   21.946023] microcode: CPU4 not a capable Intel processor
>> [   21.951678] microcode: CPU5 not a capable Intel processor
>> [   21.957326] microcode: CPU6 not a capable Intel processor
>> [   21.962935] microcode: CPU7 not a capable Intel processor
>> [   21.968611] microcode: CPU8 not a capable Intel processor
>> [   21.974212] microcode: CPU9 not a capable Intel processor
>> [   21.979842] microcode: CPU10 not a capable Intel processor
>> [   21.985577] microcode: CPU11 not a capable Intel processor
>> [   21.991323] microcode: CPU12 not a capable Intel processor
>> [   21.997055] microcode: CPU13 not a capable Intel processor
>> [   22.002774] microcode: CPU14 not a capable Intel processor
>> [   22.008460] microcode: CPU15 not a capable Intel processor
>> [   22.014600] microcode: Microcode Update Driver: v2.00 <tigran@aivazian.fsnet.co.uk>, Peter Oruba
>>
>> 2. lsmod | grep microcode
>> microcode             117749  0
>>
>> 3. rmmod microcode
>>
>> 4. dmesg logs:
>> [   64.297638] ------------[ cut here ]------------
>> [   64.302332] WARNING: at fs/sysfs/group.c:142 sysfs_remove_group+0xd9/0xe0()
>> [   64.309446] Hardware name: IBM System x -[7870C4Q]-
>> [   64.309449] sysfs group ffffffffa03a5110 not found for kobject 'cpu0'
>> [   64.309451] Modules linked in: ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf fuse loop dm_mod coretemp crc32c_intel shpchp microcode(-) cdc_ether usbnet ioatdma bnx2 mii serio_raw pcspkr pci_hotplug i2c_i801 i7core_edac i2c_core dca edac_core iTCO_wdt iTCO_vendor_support tpm_tis tpm sg tpm_bios rtc_cmos button uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif edd ext3 mbcache jbd fan processor mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
>> [   64.309499] Pid: 6529, comm: rmmod Not tainted 3.4.0-rc3-intelucodebroken-0.0.0.28.36b5ec9-default #2
>> [   64.309501] Call Trace:
>> [   64.309506]  [<ffffffff811fac69>] ? sysfs_remove_group+0xd9/0xe0
>> [   64.309510]  [<ffffffff811fac69>] ? sysfs_remove_group+0xd9/0xe0
>> [   64.309516]  [<ffffffff8103dd2a>] warn_slowpath_common+0x7a/0xb0
>> [   64.309522]  [<ffffffff8103de01>] warn_slowpath_fmt+0x41/0x50
>> [   64.309526]  [<ffffffff811f87b6>] ? sysfs_get_dirent+0x56/0x80
>> [   64.309531]  [<ffffffff811fac69>] sysfs_remove_group+0xd9/0xe0
>> [   64.309538]  [<ffffffffa03a2118>] mc_device_remove+0x78/0xa0 [microcode]
>> [   64.309545]  [<ffffffff8134b219>] subsys_interface_unregister+0x89/0xd0
>> [   64.309553]  [<ffffffffa03a357a>] microcode_exit+0x5a/0xa4 [microcode]
>> [   64.309559]  [<ffffffff810b0c8a>] sys_delete_module+0x16a/0x2b0
>> [   64.309565]  [<ffffffff810a408d>] ? trace_hardirqs_on_caller+0x12d/0x1b0
>> [   64.309573]  [<ffffffff814b36f9>] system_call_fastpath+0x16/0x1b
>> [   64.309576] ---[ end trace 748ddf8b4218f820 ]---
>>
>>
>> The above warning was repeated for each cpu, of course.
> 
> Right, this is the warning we're seeing too. Applying your patch fixes
> it, I s'pose?


Of course.. Sorry I didn't mention it explicitly.
Strictly speaking, in the patch series by Andreas,
 patch 1/2: gets rid of the warning,
 patch 2/2: ensures that the microcode module doesn't remain loaded
 when unsupported cpus are detected - but it does it only for AMD cpus.

My patch is very much like 2/2 except that it is for the Intel cpus -
if the underlying cpus are unsupported, then it ensures that the module
loading fails. [The warning is already silenced by patch 1/2].

> If so, maybe x86 people would pick it up.
> 


Ok, thanks!

Regards,
Srivatsa S. Bhat