Re: The current SME implementation fails kexec/kdump kernel booting.

[Lendacky, Thomas]

On 6/4/19 7:56 PM, Baoquan He wrote:
> On 06/04/19 at 03:56pm, Lendacky, Thomas wrote:
>> On 6/4/19 8:49 AM, Baoquan He wrote:
>>> Hi Tom,
>>>
>>> Lianbo reported kdump kernel can't boot well with 'nokaslr' added, and
>>> have to enable KASLR in kdump kernel to make it boot successfully. This
>>> blocked his work on enabling sme for kexec/kdump. And on some machines
>>> SME kernel can't boot in 1st kernel.
>>>
>>> I checked code of SME implementation, and found out the root cause. The
>>> above failures are caused by SME code, sme_encrypt_kernel(). In
>>> sme_encrypt_kernel(), you get a 2M of encryption work area as intermediate
>>> buffer to encrypt kernel in-place. And the work area is just after _end of
>>> kernel.
>>
>> I remember worrying about something like this back when I was testing the
>> kexec support. I had come up with a patch to address it, but never got the
>> time to test and submit it.  I've included it here if you'd like to test
>> it (I haven't done run this patch in quite some time). If it works, we can
>> think about submitting it.
> 
> Thanks for your quick response and making this patch, Tom.
> 
> Tested on a speedway machine, it entered into kernel, but failed in
> below stage. Tested two times, always happened.

Is this the initial kernel boot or the kexec kernel boot?

It looks like this is related to the initrd/initramfs decryption. Not
sure what could be happening there. I just tried the patch on my Naples
system and a 5.2.0-rc3 kernel and have been able to repeatedly kexec boot
a number of times so far.

Thanks,
Tom

> 
> 
> [    4.978521] Freeing unused decrypted memory: 2040K
> [    4.983800] Freeing unused kernel image memory: 2344K
> [    4.988943] Write protecting the kernel read-only data: 18432k
> [    4.995306] Freeing unused kernel image memory: 2012K
> [    5.000488] Freeing unused kernel image memory: 256K
> [    5.005540] Run /init as init process
> [    5.009443] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
> [    5.017230] CPU: 0 PID: 1 Comm: init Not tainted 5.2.0-rc2+ #38
> [    5.023251] Hardware name: AMD Corporation Speedway/Speedway, BIOS RSW1004B 10/18/2017
> [    5.031299] Call Trace:
> [    5.033793]  dump_stack+0x46/0x60
> [    5.037169]  panic+0xfb/0x2cb
> [    5.040191]  do_exit.cold.21+0x59/0x81
> [    5.044004]  do_group_exit+0x3a/0xa0
> [    5.047640]  __x64_sys_exit_group+0x14/0x20
> [    5.051899]  do_syscall_64+0x55/0x1c0
> [    5.055627]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [    5.060764] RIP: 0033:0x7fa1b1fc9e2e
> [    5.064404] Code: Bad RIP value.
> [    5.067687] RSP: 002b:00007fffc5abb778 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
> [    5.075296] RAX: ffffffffffffffda RBX: 00007fa1b1fd2528 RCX: 00007fa1b1fc9e2e
> [    5.082625] RDX: 000000000000007f RSI: 000000000000003c RDI: 000000000000007f
> [    5.089879] RBP: 00007fa1b21d8d00 R08: 00000000000000e7 R09: 00007fffc5abb688
> [    5.097134] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002
> [    5.104386] R13: 0000000000000001 R14: 00007fa1b21d8d40 R15: 00007fa1b21d8d30
> [    5.111645] Kernel Offset: disabled
> [    5.423002] Rebooting in 10 seconds..
> [   15.429641] ACPI MEMORY or I/O RESET_REG.
>