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

diff --git a/arch/x86/boot/startup/gdt_idt.c b/arch/x86/boot/startup/gdt_idt.c
index 7e34d0b426b11002d2286a2b23e822a13a0c4f66..a3112a69b06a77a1ca4cc5ece40a1218092012f5 100644 (file)
--- 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 ad9212df0ec0cba13ceed1b91a061b7339245464..6324f4c6c54571c2fbe94c4c65cabe288ed6d4d6 100644 (file)
--- 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 6b68a206fa7f527c98e97007945cf62942aa1106..29226f3ac06477e3c348c5f899d8fe9426b9b0e9 100644 (file)
--- 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);
+}