[Xen-devel] A useless short jmp?

["Li, Xin B" <xin.b.li@xxxxxxxxx>]

In trampoline.S we have a short jmp after lmsw:

trampoline_realmode_entry:
        mov     %cs,%ax
        mov     %ax,%ds
        movb    $0xA5,bootsym(trampoline_cpu_started)
        cld
        cli
        lidt    bootsym(idt_48)
        lgdt    bootsym(gdt_48)
        xor     %ax, %ax
        inc     %ax
        lmsw    %ax                       # CR0.PE = 1 (enter protected
mode)
        mov     $1,%bl                    # EBX != 0 indicates we are an
AP
        jmp     1f
1:      ljmpl   $BOOT_CS32,$bootsym_phys(trampoline_protmode_entry)

According to Intel Spec, it's useless, do we have any special reason to
have it there?
BTW why put mov $1, %bl between lmsw and it's corresponding ljmp?
thanks
-Xin

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