linux-kernel - [RFC PATCH PoC 02/11] x86/boot: Move early_setup

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Message-ID: <20250423110948.1103030-15-ardb+git@google.com>
Date: Wed, 23 Apr 2025 13:09:51 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org, mingo@...nel.org, Ard Biesheuvel <ardb@...nel.org>
Subject: [RFC PATCH PoC 02/11] x86/boot: Move early_setup_gdt() back into head64.c

From: Ard Biesheuvel <ardb@...nel.org>

Move early_setup_gdt() out of the startup code that is callable from the
1:1 mapping - this is not needed, and instead, it is better to expose
the helper that does reside in __head directly. This reduces the amount
of code that needs special checks for 1:1 execution suitability.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/boot/startup/gdt_idt.c | 15 +--------------
 arch/x86/include/asm/setup.h    |  1 +
 arch/x86/kernel/head64.c        | 12 ++++++++++++
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/arch/x86/boot/startup/gdt_idt.c b/arch/x86/boot/startup/gdt_idt.c
index 7e34d0b426b1..a3112a69b06a 100644
--- a/arch/x86/boot/startup/gdt_idt.c
+++ b/arch/x86/boot/startup/gdt_idt.c
@@ -24,7 +24,7 @@
 static gate_desc bringup_idt_table[NUM_EXCEPTION_VECTORS] __page_aligned_data;
 
 /* This may run while still in the direct mapping */
-static void __head startup_64_load_idt(void *vc_handler)
+void __head startup_64_load_idt(void *vc_handler)
 {
 	struct desc_ptr desc = {
 		.address = (unsigned long)rip_rel_ptr(bringup_idt_table),
@@ -43,19 +43,6 @@ static void __head startup_64_load_idt(void *vc_handler)
 	native_load_idt(&desc);
 }
 
-/* This is used when running on kernel addresses */
-void early_setup_idt(void)
-{
-	void *handler = NULL;
-
-	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
-		setup_ghcb();
-		handler = vc_boot_ghcb;
-	}
-
-	startup_64_load_idt(handler);
-}
-
 /*
  * Setup boot CPU state needed before kernel switches to virtual addresses.
  */
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index ad9212df0ec0..6324f4c6c545 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -52,6 +52,7 @@ extern void reserve_standard_io_resources(void);
 extern void i386_reserve_resources(void);
 extern unsigned long __startup_64(unsigned long p2v_offset, struct boot_params *bp);
 extern void startup_64_setup_gdt_idt(void);
+extern void startup_64_load_idt(void *vc_handler);
 extern void early_setup_idt(void);
 extern void __init do_early_exception(struct pt_regs *regs, int trapnr);
 
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 6b68a206fa7f..29226f3ac064 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -303,3 +303,15 @@ void __init __noreturn x86_64_start_reservations(char *real_mode_data)
 
 	start_kernel();
 }
+
+void early_setup_idt(void)
+{
+	void *handler = NULL;
+
+	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
+		setup_ghcb();
+		handler = vc_boot_ghcb;
+	}
+
+	startup_64_load_idt(handler);
+}
-- 
2.49.0.805.g082f7c87e0-goog