[RFC PATCH PoC 02/11] x86/boot: Move early_setup_gdt() back into head64.c

Ard Biesheuvel
2025-04-23T11:10:40Z

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@kernel.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