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Subject: Re: Boot regression with bacf6b499e11 ("x86/mm: Use a struct to
 reduce parameters for SME PGD mapping") on top of -rc8
From:   Laura Abbott <labbott@redhat.com>
To:     Tom Lendacky <thomas.lendacky@amd.com>,
        Gabriel C <nix.or.die@gmail.com>
Cc:     Borislav Petkov <bp@suse.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Brijesh Singh <brijesh.singh@amd.com>, X86 ML <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date:   Fri, 19 Jan 2018 23:03:27 -0800
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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@redhat.com>:
>>>> On 01/19/2018 06:23 PM, Gabriel C wrote:
>>>>>
>>>>> 2018-01-20 2:23 GMT+01:00 Laura Abbott <labbott@redhat.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