Message-ID: <CAEJqkghdBbah_XkrsOKOofLugPRioXx6ud+2Fq0_SyP-O68ULQ@mail.gmail.com>
Date:   Sat, 20 Jan 2018 13:08:02 +0100
From:   Gabriel C <nix.or.die@...il.com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Borislav Petkov <bp@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Brijesh Singh <brijesh.singh@....com>, X86 ML <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Boot regression with bacf6b499e11 ("x86/mm: Use a struct to
 reduce parameters for SME PGD mapping") on top of -rc8

2018-01-20 8:03 GMT+01:00 Laura Abbott <labbott@...hat.com>:
> On 01/19/2018 10:57 PM, Laura Abbott wrote:
>>
>> On 01/19/2018 10:15 PM, Tom Lendacky wrote:
>>>
>>> On 1/19/2018 11:25 PM, Gabriel C wrote:
>>>>
>>>> 2018-01-20 5:02 GMT+01:00 Laura Abbott <labbott@...hat.com>:
>>>>>
>>>>> On 01/19/2018 06:23 PM, Gabriel C wrote:
>>>>>>
>>>>>>
>>>>>> 2018-01-20 2:23 GMT+01:00 Laura Abbott <labbott@...hat.com>:
>>>>>>>
>>>>>>>
>>>>>>> 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 )..
>>>
>>>
>>
>> The machines I have are a Lenovo X1 Carbon and a Lenovo T470s.
>> A Lenovo X220 ThinkPad also reported the problem.
>>
>> If I comment out sme_encrypt_kernel it boots:
>>
>> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
>> index 7ba5d819ebe3..443ef5d3f1fa 100644
>> --- a/arch/x86/kernel/head64.c
>> +++ b/arch/x86/kernel/head64.c
>> @@ -158,7 +158,7 @@ unsigned long __head __startup_64(unsigned long
>> physaddr,
>>          *p += load_delta - sme_get_me_mask();
>>
>>          /* Encrypt the kernel and related (if SME is active) */
>> -       sme_encrypt_kernel(bp);
>> +       //sme_encrypt_kernel(bp);
>>
>>          /*
>>           * Return the SME encryption mask (if SME is active) to be used
>> as a
>>
>>
>> Interestingly, I tried to print the values in sme_active
>> (sme_me_mask , sev_enabled) followed by a return at the
>> very start of sme_encrypt_kernel and that rebooted as well,
>> vs booting if I just kept the return. sme_me_mask and
>> sev_enabled are explicitly marked as being in .data,
>> is it possible they are ending up in a section that isn't
>> yet mapped or did I hit print too early?
>>
>> Thanks,
>> Laura
>>
>
> One last note: This was built with gcc 7.2.1

With retpoline patches ( if so what patchset ) ? or the one from gcc7 branch ?

I didn't tested with this gcc version , I've tested with gcc6 and
gcc8-retpoline-enabled compiler.

Regards,

Gabriel

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