Linux kernel fails to boot after "Set boot script outside SMM after SmmReadyToLock"

[Hristo Mihaylov <hristo.mihaylov@prodrive-technologies.com>]

Hello,

I'm building a custom x86_64 platform. It gets to BDS, where I select an USB with Debian as a boot device.

```
[Bds]Booting UEFI USB Flash Memory C412F52D6C89C0210002C15B
error: no suitable video mode found.
error: no video mode activated.



                         GNU GRUB  version 2.02~beta3-5

/----------------------------------------------------------------------------\
| Graphical install                                                          |
|*Install                                                                    |
| Advanced options ...                                                       |
| Install with speech synthesis                                              |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
\----------------------------------------------------------------------------/
      Use the ^ and v keys to select which entry is highlighted.
      Press enter to boot the selected OS, `e' to edit the commands
      before booting or `c' for a command-line.



                         GNU GRUB  version 2.02~beta3-5

/----------------------------------------------------------------------------\
|setparams 'Install'                                                         |
|                                                                            |
|    set background_color=black                                              |
|    linux    /install.amd/vmlinuz console=ttyS0,115200                      |
|    initrd   /install.amd/initrd.gz                                         |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
|                                                                            |
\----------------------------------------------------------------------------/

      Minimum Emacs-like screen editing is supported. TAB lists
      completions. Press Ctrl-x or F10 to boot, Ctrl-c or F2 for a
      command-line or ESC to discard edits and return to the GRUB menu.
  Booting a command list

error: no suitable video mode found.
Booting in blind mode
```

Here I set the serial console as a display device. Then I continue into booting the USB stick where I see 2 fatal errors.
Afterwhich, the kernel starts booting, but fails to boot completely with no error message or anything. The last few lines
Discover SATA devices.

```
OnExitBootServices..
IioInit Late Secure the Platform (TXT)..
S3BootScriptSaveMemWrite called
FATAL ERROR: Set boot script outside SMM after SmmReadyToLock!!!
S3BootScriptSaveMemWrite called
FATAL ERROR: Set boot script outside SMM after SmmReadyToLock!!!
SmmInstallProtocolInterface: 296EB418-C4C8-4E05-AB59-39E8AF56F00A 0
SmmLockBoxSmmLib RestoreLockBox - Enter
SmmLockBoxSmmLib RestoreLockBox - Exit (Success)
SmmLockBoxSmmLib SaveLockBox - Enter
LockBoxGuid - B5AF1D7A-B8CF-4EB3-8925-A820E16B687D, SmramBuffer - 0x76F49000, Length - 0x36F6
SmmLockBoxSmmLib SaveLockBox - Exit (Success)
SmmLockBoxSmmLib SaveLockBox - Enter
LockBoxGuid - 627EE2DA-3BF9-439B-929F-2E0E6E9DBA62, SmramBuffer - 0x76F48000, Length - 0x18
SmmLockBoxSmmLib SaveLockBox - Exit (Success)
SmmLockBoxSmmLib SetLockBoxAttributes - Enter
SmmLockBoxSmmLib SetLockBoxAttributes - Exit (Success)
[    0.000000] Linux version 4.9.0-6-amd64 (debian-kernel@lists.debian.org) (gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1) ) #1 SMP Debian 4.9.82-1+deb9u3 (2018-03-02)
[    0.000000] Command line: BOOT_IMAGE=/install.amd/vmlinuz console=ttyS0,115200
[    0.000000] Intel Spectre v2 broken microcode detected; disabling Speculation Control
```

Is this related to the SMM fatal errors? It's occurring here https://github.com/tianocore/edk2/blob/14923c1a6bf9940b48feeaf47cb5d6c662b6528c/MdeModulePkg/Library/PiDxeS3BootScriptLib/BootScriptSave.c#L829
There a lot of function calls and I can't print a stack trace.

If this is related to the SMM errors, any advice on how to fix them? If not, I guess it's off to the Debian mailing lists.

Regards,
Hristo Mihaylov