linux-kernel - [tip: x86/boot] x86/boot: Move early_setup

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Message-ID: <174636842987.22196.4991784786092668294.tip-bot2@tip-bot2>
Date: Sun, 04 May 2025 14:20:29 -0000
From: "tip-bot2 for Ard Biesheuvel" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>,
 Arnd Bergmann <arnd@...db.de>, David Woodhouse <dwmw@...zon.co.uk>,
 Dionna Amalie Glaze <dionnaglaze@...gle.com>,
 "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>,
 Kevin Loughlin <kevinloughlin@...gle.com>, Len Brown <len.brown@...el.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 Tom Lendacky <thomas.lendacky@....com>, linux-efi@...r.kernel.org,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/boot] x86/boot: Move early_setup_gdt() back into head64.c

The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     bd4a58beaaf1f4aff025282c6e8b130bdb4a29e4
Gitweb:        https://git.kernel.org/tip/bd4a58beaaf1f4aff025282c6e8b130bdb4a29e4
Author:        Ard Biesheuvel <ardb@...nel.org>
AuthorDate:    Sun, 04 May 2025 11:52:31 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sun, 04 May 2025 15:27:23 +02:00

x86/boot: Move early_setup_gdt() back into head64.c

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. In particular, it avoids dealing with the GHCB
page (and its physical address) in startup code, which runs from the
1:1 mapping, making physical to virtual translations ambiguous.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Dionna Amalie Glaze <dionnaglaze@...gle.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Kevin Loughlin <kevinloughlin@...gle.com>
Cc: Len Brown <len.brown@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: linux-efi@...r.kernel.org
Link: https://lore.kernel.org/r/20250504095230.2932860-26-ardb+git@google.com
---
 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 7e34d0b..a3112a6 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 ad9212d..6324f4c 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 6b68a20..29226f3 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);
+}