Re: Boot regression with bacf6b499e11 ("x86/mm: Use a struct to reduce parameters for SME PGD mapping") on top of -rc8

[Tom Lendacky]

On 1/19/2018 11:25 PM, Gabriel C wrote:
> 2018-01-20 5:02 GMT+01:00 Laura Abbott <labbott@xxxxxxxxxx>:
>> On 01/19/2018 06:23 PM, Gabriel C wrote:
>>>
>>> 2018-01-20 2:23 GMT+01:00 Laura Abbott <labbott@xxxxxxxxxx>:
>>>>
>>>> Hi,
>>>
>>>
>>> Hi ,
>>>
>>>>
>>>> Fedora got multiple reports of an early bootup crash post -rc8.
>>>> Bisection showed bacf6b499e11 ("x86/mm: Use a struct to reduce
>>>> parameters for SME PGD mapping") . It doesn't revert cleanly
>>>> but if I revert the few other changes in arch/x86/mm/mem_encrypt.c
>>>> as well it boots up fine.
>>>>
>>>> Annoyingly, I can't seem to get any actual kernel logs even with
>>>> earlyprintk. It just reboots immediately (triple fault?). This
>>>> happens on both of my Lenovo machines and I can ask other reporters
>>>> for details as well.
>>>>
>>>
>>> I tested these patches on 2 Lenovo Ideapad both with Skylake CPUs
>>> on a older dual Xeon box , on 2 Toshibas with AMD APUs , on a RYZEN box ,
>>> on dual EPYC box .. ofc on EPYC with mem_encrypt=on on the Intel CPUs
>>> disabled.
>>>
>>> Also tested on top 4.14.13 , 4.14.14 as well on top 4.15.0-rc7 and on
>>> current master/rc8++ without to see something like this.
>>>
>>> Also we pushed these patches on 4.14.13/14 and didn't got any reports
>>> about
>>> something like this.
>>>
>>> What Lenovo boxes are these ? maybe I find one to reproduce.
>>>
>>>
>>>> $ git bisect log
>>>> # bad: [ec835f8104a21f4d4eeb9d316ee71d2b4a7f00de] Merge tag
>>>> 'trace-v4.15-rc4-3' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
>>>> # good: [a8750ddca918032d6349adbf9a4b6555e7db20da] Linux 4.15-rc8
>>>> git bisect start 'origin/master' 'v4.15-rc8'
>>>> # bad: [79683f80e4f07dba13cc08d0ebcf5c7b0aa1bf68] Merge tag
>>>> 'mmc-v4.15-rc2-3' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc
>>>> git bisect bad 79683f80e4f07dba13cc08d0ebcf5c7b0aa1bf68
>>>> # good: [161f72ed6dbe7fb176585091d3b797125d310399] Merge tag
>>>> 'mac80211-for-davem-2018-01-15' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211
>>>> git bisect good 161f72ed6dbe7fb176585091d3b797125d310399
>>>> # good: [88dc7fca18001fd883e5ace775afa316b68c8f2c] Merge branch
>>>> 'x86-pti-for-linus' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>>> git bisect good 88dc7fca18001fd883e5ace775afa316b68c8f2c
>>>> # bad: [d47924417319e3b6a728c0b690f183e75bc2a702] x86/intel_rdt/cqm:
>>>> Prevent
>>>> use after free
>>>> git bisect bad d47924417319e3b6a728c0b690f183e75bc2a702
>>>> # good: [fc90ccfd286eabb05ec54521367df8663cf0bbbf] Revert "x86/apic:
>>>> Remove
>>>> init_bsp_APIC()"
>>>> git bisect good fc90ccfd286eabb05ec54521367df8663cf0bbbf
>>>> # bad: [bacf6b499e11760aef73a3bb5ce4e5eea74a3fd4] x86/mm: Use a struct to
>>>> reduce parameters for SME PGD mapping
>>>> git bisect bad bacf6b499e11760aef73a3bb5ce4e5eea74a3fd4
>>>> # good: [1303880179e67c59e801429b7e5d0f6b21137d99] x86/mm: Clean up
>>>> register
>>>> saving in the __enc_copy() assembly code
>>>> git bisect good 1303880179e67c59e801429b7e5d0f6b21137d99
>>>> # first bad commit: [bacf6b499e11760aef73a3bb5ce4e5eea74a3fd4] x86/mm:
>>>> Use a
>>>> struct to reduce parameters for SME PGD mapping
>>>>
>>>>
>>>> Configuration is at
>>>>
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git/commit/?h=rawhide
>>>> Note that I do think this is something in the Fedora configuration
>>>> because a generic "make defconfig" booted just fine.
>>>
>>>
>>> But maybe some of the Fedora patches ?
>>>
>>> Can you try an kernel with the config but without any patches ?
>>> Or a defconfig and just enable  CONFIG_AMD_MEM_ENCRYPT ?
>>>
>>
>> The bisect was a vanilla kernel without Fedora patches.
> 
> Ok . I did an build ( v4.15-rc8-225-g8dd903d2cf7b ) on my AMD
> Workstation  ( EPYC CPU )

I've tried multiple config combinations on my EPYC system and have not
been able to reproduce this issue and have not had any boot issues with
mem_encrypt=on or mem_encrypt=off.  I don't have access to a non-AMD box
at the moment, but I'm really scratching my head on this one.

>  with your 64bit config and one on the Ideapad ( Intel i7-6498DU ) ..
> I disabled Selinux since I don't use it here and module  signing.
> 
> Also with your config my serial setup won't work and the kernel hangs
> but mem_encrypt=on/off works just fine.

If your using the EPYC serial device and you haven't enabled legacy
serial device support (if your BIOS supports that), then you're using
it as a platform device.  The fedora config has not set the
CONFIG_X86_AMD_PLATFORM_DEVICE setting so you won't get the module
to load and give you serial output.

I'm confused when you say the kernel hangs but mem_encrypt=on/off works
just fine, can you explain that a bit more?

> 
> Also I notice on the Workstation it takes forever to boot untill
> 'DMA-API' reports out-of-memory
> ( dunno how much memory it need but the box has 128GB of RAM )..

I haven't seen this before.

Thanks,
Tom

> 
> 
> Can you tell us your Lenovo models  please  ?
> 
> Reagrds,
> 
> Gabriel C
>