x86, reboot: Drop redundant write of reboot_mode

We write reboot_mode to BIOS location 0x472 in
native_machine_emergency_restart() (reboot.c:542) already, there is no
need to then write it again in machine_real_restart().

This means nothing gets written there for MRR_APM, but the APM call is
a poweroff call and doesn't use this memory location.

Link: http://lkml.kernel.org/n/tip-3i0pfh44c1e3jv5lab0cf7sc@git.kernel.org
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 6ddb9cd0ced0d11bd888c03bc939ed9265f6c0eb..6ef559f09acd3b18068ab889403b7c30ff6e6f20 100644 (file)
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -179,14 +179,6 @@ void __noreturn machine_real_restart(unsigned int type)
        write_cr3(real_mode_header->trampoline_pgd);
 #endif
 
-       /*
-        * Write 0x1234 to absolute memory location 0x472.  The BIOS reads
-        * this on booting to tell it to "Bypass memory test (also warm
-        * boot)".  This seems like a fairly standard thing that gets set by
-        * REBOOT.COM programs, and the previous reset routine did this
-        * too. */
-       *((unsigned short *)0x472) = reboot_mode;
-
        /* Jump to the identity-mapped low memory code */
 #ifdef CONFIG_X86_32
        asm volatile("jmpl *%0" : :