Re: [Intel-gfx] alderlake crashes (random memory corruption?) with 6.0 i915 / ucode related

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

+ Jani and Ville for the intel_bios.c warn - no idea if that is relevant.

Hi,

On 15/10/2022 15:25, Hans de Goede wrote:
> Hi,
> 
> On 10/13/22 22:33, Hans de Goede wrote:
>> Hi All,
>>
>> Yesterday I got a new Lenovo ThinkPad X1 yoga gen 7 laptop, since I plan
>> to make this my new day to day laptop I have copied over the entire
>> rootfs, /home, etc. from my current laptop to avoid having to tweak
>> everything to my liking again.
>>
>> This meant I had an initramfs generated for the other laptop. Which should
>> be fine since both are Intel machines and the old 5.19.y initramfs-es
>> worked fine. But 6.0.0 crashed with what seems like random memory
>> corruption (list integrity checks failing) until I regenerated the initrd ...
>>
>> Comparing the old vs regenerated initrds showed no relevant differences,
>> which made me think this is a CPU ucode issue (which is pre-fixed
>> to the initrd for early microcode loading).
>>
>> After some tests I have the following obeservations with 6.0.0:
>>
>> 1. The least stable is the old initrd (so with the wrong
>> ucode prefixed) this crashes before ever reaching gdm.
>> I believe that this is caused by late microcode loading
>> kicking in in this case (I though that was being removed?)
>> and doing load microcode loading on the i7-1260P with its
>> mix of P + E cores seems to seriously mess things up.
>>
>> 2. Slightly more stable, lasting at least a few minutes
>> before crashing is using dis_ucode_ldr
>>
>> 3. Using nomodeset seems to stabilize things even with
>> the old initrd with the wrong microcode prefixed
>>
>> 4. 5.19, with an old initrd and with normal modesetting
>> enabled works fine, so in a way this is a 6.0.0 regression
>>
>> 5. Using 6.0 with the new initrd with the new microcode
>> seems mostly stable, although sometimes this seems to
>> hang very early during boot, esp. if a previous boot
>> crashed and I have not run this for a long time yet.
>>
>> 6. After crashes it seems to be necessary to powercycle
>> the machine to get things back in working condition.
>>
>>
>> With 6.0 the following WARN triggers:
>> drivers/gpu/drm/i915/display/intel_bios.c:477:
>>
>>          drm_WARN(&i915->drm, min_size == 0,
>>                   "Block %d min_size is zero\n", section_id);
>>
>> Since nomodeset helps this might be quite relevant, in 5.19.13
>> this does not happen, but I'm not sure if 5.19 has this check
>> at all.
>>
>>
>> There is a 2022/10/07 BIOS update which includes a CPU microcode
>> update available from Lenovo, I have not applied this yet in case
>> people want to investigate this further first.
> 
> A quick update on this, the microcode being in the initrd or not
> seems to be a bit of a red herring. Yesterday the machine crashed
> twice at boot with 6.0.0 with an initrd which did correctly have
> the alderlake microcode cpio archive prefixed.
> 
> Where as with 5.19 it boots correctly everytime. I will try to
> make some time to git bisect this sometime next week. I expect
> this is an i915 issue though since 6.0.0 with nomodeset on
> the cmdline does seem to boot successfully every time.

Maybe try with KASAN to see if it catches something before random list 
corruption starts happening?

Regards,

Tvrtko