[tip: smp/core] x86/smpboot: Restrict soft_restart_cpu() to SEV

["tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>]

The following commit has been merged into the smp/core branch of tip:

Commit-ID:     cded367976587ed4d160ed7d6bb118992a8b82ab
Gitweb:        https://git.kernel.org/tip/cded367976587ed4d160ed7d6bb118992a8b82ab
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Fri, 12 May 2023 23:07:08 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 15 May 2023 13:44:50 +02:00

x86/smpboot: Restrict soft_restart_cpu() to SEV

Now that the CPU0 hotplug cruft is gone, the only user is AMD SEV.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205255.822234014@linutronix.de
---
 arch/x86/kernel/callthunks.c |  2 +-
 arch/x86/kernel/head_32.S    | 14 --------------
 arch/x86/kernel/head_64.S    |  2 +-
 3 files changed, 2 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index f5a6236..8bb9373 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -133,7 +133,7 @@ static bool skip_addr(void *dest)
 	/* Accounts directly */
 	if (dest == ret_from_fork)
 		return true;
-#ifdef CONFIG_HOTPLUG_CPU
+#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_AMD_MEM_ENCRYPT)
 	if (dest == soft_restart_cpu)
 		return true;
 #endif
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 805abf1..c931899 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -138,20 +138,6 @@ SYM_CODE_START(startup_32)
 	jmp .Ldefault_entry
 SYM_CODE_END(startup_32)
 
-#ifdef CONFIG_HOTPLUG_CPU
-/*
- * Entry point for soft restart of a CPU. Invoked from xxx_play_dead() for
- * restarting the boot CPU or for restarting SEV guest CPUs after CPU hot
- * unplug. Everything is set up already except the stack.
- */
-SYM_FUNC_START(soft_restart_cpu)
-	movl initial_stack, %ecx
-	movl %ecx, %esp
-	call *(initial_code)
-1:	jmp 1b
-SYM_FUNC_END(soft_restart_cpu)
-#endif
-
 /*
  * Non-boot CPU entry point; entered from trampoline.S
  * We can't lgdt here, because lgdt itself uses a data segment, but
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index fc86bc1..8458033 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -375,7 +375,7 @@ SYM_CODE_END(secondary_startup_64)
 #include "verify_cpu.S"
 #include "sev_verify_cbit.S"
 
-#ifdef CONFIG_HOTPLUG_CPU
+#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_AMD_MEM_ENCRYPT)
 /*
  * Entry point for soft restart of a CPU. Invoked from xxx_play_dead() for
  * restarting the boot CPU or for restarting SEV guest CPUs after CPU hot