Merge tag 'x86-boot-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 boot updates from Ingo Molnar:

 - Ignore NMIs during very early boot, to address kexec crashes

 - Remove redundant initialization in boot/string.c's strcmp()

* tag 'x86-boot-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/boot: Remove redundant initialization of the 'delta' variable in strcmp()
  x86/boot: Ignore NMIs during very early boot

Author: torvalds

arch/x86/boot/compressed/ident_map_64.c

@@ -386,3 +386,8 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
 	 */
 	kernel_add_identity_map(address, end);
 }
+
+void do_boot_nmi_trap(struct pt_regs *regs, unsigned long error_code)
+{
+	/* Empty handler to ignore NMI during early boot */
+}

arch/x86/boot/compressed/idt_64.c

@@ -61,6 +61,7 @@ void load_stage2_idt(void)
 	boot_idt_desc.address = (unsigned long)boot_idt;
 
 	set_idt_entry(X86_TRAP_PF, boot_page_fault);
+	set_idt_entry(X86_TRAP_NMI, boot_nmi_trap);
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 	/*

arch/x86/boot/compressed/idt_handlers_64.S

@@ -70,6 +70,7 @@ SYM_FUNC_END(\name)
 	.code64
 
 EXCEPTION_HANDLER	boot_page_fault do_boot_page_fault error_code=1
+EXCEPTION_HANDLER	boot_nmi_trap do_boot_nmi_trap error_code=0
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 EXCEPTION_HANDLER	boot_stage1_vc do_vc_no_ghcb		error_code=1

arch/x86/boot/compressed/misc.h

@@ -196,6 +196,7 @@ static inline void cleanup_exception_handling(void) { }
 
 /* IDT Entry Points */
 void boot_page_fault(void);
+void boot_nmi_trap(void);
 void boot_stage1_vc(void);
 void boot_stage2_vc(void);
 

arch/x86/boot/string.c

@@ -49,7 +49,7 @@ int strcmp(const char *str1, const char *str2)
 {
 	const unsigned char *s1 = (const unsigned char *)str1;
 	const unsigned char *s2 = (const unsigned char *)str2;
-	int delta = 0;
+	int delta;
 
 	while (*s1 || *s2) {
 		delta = *s1 - *s2;