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

tip-bot2 for Ard Biesheuvel
2025-05-04T14:20:31Z

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@kernel.org>
AuthorDate: Sun, 04 May 2025 11:52:31 +02:00
Committer: Ingo Molnar <mingo@kernel.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@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.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);
+}