linux-kernel - sev_es_trampoline_start undefined symbol referenced errors during kunit run

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Message-ID: <7c5f9e2a-2e9d-46f2-89b2-83e0d68d3113@linuxfoundation.org>
Date: Mon, 14 Apr 2025 16:28:44 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: thomas.lendacky@....com
Cc: David Gow <davidgow@...gle.com>, Shuah Khan <skhan@...uxfoundation.org>,
 "x86@...nel.org" <x86@...nel.org>,
 Brendan Higgins <brendan.higgins@...ux.dev>, linux-kernel@...r.kernel.org,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>
Subject: sev_es_trampoline_start undefined symbol referenced errors during
 kunit run

Hi Tom,

I have been seeing sev_es_trampoline_start undefined symbol referenced errors
during the following kunit test runs.

./tools/testing/kunit/kunit.py run --arch x86_64
./tools/testing/kunit/kunit.py run --alltests --arch x86_64

The error is here:

ERROR:root:ld:arch/x86/realmode/rm/realmode.lds:236: undefined symbol `sev_es_trampoline_start' referenced in expression
make[6]: *** [../arch/x86/realmode/rm/Makefile:49: arch/x86/realmode/rm/realmode.elf] Error 1
make[5]: *** [../arch/x86/realmode/Makefile:22: arch/x86/realmode/rm/realmode.bin] Error 2
make[4]: *** [../scripts/Makefile.build:461: arch/x86/realmode] Error 2

I made time to look into this error.

sev_es_trampoline_start is referenced in arch/x86/coco/sev/core.c twice:

- To override start_ip in  wakeup_cpu_via_vmgexit()
- In sev_es_setup_ap_jump_table() to compute startup_ip

sev_es_trampoline_start is defined if CONFIG_AMD_MEM_ENCRYPT is enabled
and all other references to it are under ifdef CONFIG_AMD_MEM_ENCRYPT
conditional except the two in arch/x86/coco/sev/core.c

git grep sev_es_trampoline_start
arch/x86/coco/sev/core.c:       start_ip = real_mode_header->sev_es_trampoline_start;
arch/x86/coco/sev/core.c:       startup_ip = (u16)(rmh->sev_es_trampoline_start -
arch/x86/include/asm/realmode.h:        u32     sev_es_trampoline_start;
arch/x86/realmode/rm/header.S:  .long   pa_sev_es_trampoline_start
arch/x86/realmode/rm/trampoline_64.S:SYM_CODE_START(sev_es_trampoline_start)
arch/x86/realmode/rm/trampoline_64.S:SYM_CODE_END(sev_es_trampoline_start)

Why are these references not under ifdef CONFIG_AMD_MEM_ENCRYPT conditional?

The following commits added the references to sev_es_trampoline_start
in arch/x86/coco/sev/core.c

0afb6b660a6b58cb336d1175ed687bf9525849a4
8940ac9ced8bc1c48c4e28b0784e3234c9d14469

thanks,
-- Shuah