x86-64, reboot: Allow reboot=bios and reboot-cpu override on x86-64

With the revamped realmode trampoline code, it is trivial to extend
support for reboot=bios to x86-64.  Furthermore, while we are at it,
remove the restriction that only we can only override the reboot CPU
on 32 bits.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/n/tip-jopx7y6g6dbcx4tpal8q0jlr@git.kernel.org

1 files changed, 0 insertions, 132 deletions

diff --git a/arch/x86/realmode/rm/reboot_32.S b/arch/x86/realmode/rm/reboot_32.S
deleted file mode 100644
index 114044876b3d..000000000000
--- a/arch/x86/realmode/rm/reboot_32.S
+++ /dev/null
@@ -1,132 +0,0 @@
-#include <linux/linkage.h>
-#include <linux/init.h>
-#include <asm/segment.h>
-#include <asm/page_types.h>
-#include "realmode.h"
-
-/*
- * The following code and data reboots the machine by switching to real
- * mode and jumping to the BIOS reset entry point, as if the CPU has
- * really been reset.  The previous version asked the keyboard
- * controller to pulse the CPU reset line, which is more thorough, but
- * doesn't work with at least one type of 486 motherboard.  It is easy
- * to stop this code working; hence the copious comments.
- *
- * This code is called with the restart type (0 = BIOS, 1 = APM) in %eax.
- */
-	.section ".text32", "ax"
-	.code32
-
-	.balign	16
-ENTRY(machine_real_restart_asm)
-	/* Set up the IDT for real mode. */
-	lidtl	pa_machine_real_restart_idt
-
-	/*
-	 * Set up a GDT from which we can load segment descriptors for real
-	 * mode.  The GDT is not used in real mode; it is just needed here to
-	 * prepare the descriptors.
-	 */
-	lgdtl	pa_machine_real_restart_gdt
-
-	/*
-	 * Load the data segment registers with 16-bit compatible values
-	 */
-	movl	$16, %ecx
-	movl	%ecx, %ds
-	movl	%ecx, %es
-	movl	%ecx, %fs
-	movl	%ecx, %gs
-	movl	%ecx, %ss
-	ljmpw	$8, $1f
-
-/*
- * This is 16-bit protected mode code to disable paging and the cache,
- * switch to real mode and jump to the BIOS reset code.
- *
- * The instruction that switches to real mode by writing to CR0 must be
- * followed immediately by a far jump instruction, which set CS to a
- * valid value for real mode, and flushes the prefetch queue to avoid
- * running instructions that have already been decoded in protected
- * mode.
- *
- * Clears all the flags except ET, especially PG (paging), PE
- * (protected-mode enable) and TS (task switch for coprocessor state
- * save).  Flushes the TLB after paging has been disabled.  Sets CD and
- * NW, to disable the cache on a 486, and invalidates the cache.  This
- * is more like the state of a 486 after reset.  I don't know if
- * something else should be done for other chips.
- *
- * More could be done here to set up the registers as if a CPU reset had
- * occurred; hopefully real BIOSs don't assume much.  This is not the
- * actual BIOS entry point, anyway (that is at 0xfffffff0).
- *
- * Most of this work is probably excessive, but it is what is tested.
- */
-	.text
-	.code16
-
-	.balign	16
-machine_real_restart_asm16:
-1:
-	xorl	%ecx, %ecx
-	movl	%cr0, %edx
-	andl	$0x00000011, %edx
-	orl	$0x60000000, %edx
-	movl	%edx, %cr0
-	movl	%ecx, %cr3
-	movl	%cr0, %edx
-	testl	$0x60000000, %edx	/* If no cache bits -> no wbinvd */
-	jz	2f
-	wbinvd
-2:
-	andb	$0x10, %dl
-	movl	%edx, %cr0
-	LJMPW_RM(3f)
-3:
-	andw	%ax, %ax
-	jz	bios
-
-apm:
-	movw	$0x1000, %ax
-	movw	%ax, %ss
-	movw	$0xf000, %sp
-	movw	$0x5307, %ax
-	movw	$0x0001, %bx
-	movw	$0x0003, %cx
-	int	$0x15
-	/* This should never return... */
-
-bios:
-	ljmpw	$0xf000, $0xfff0
-
-	.section ".rodata", "a"
-
-	.balign	16
-GLOBAL(machine_real_restart_idt)
-	.word	0xffff		/* Length - real mode default value */
-	.long	0		/* Base - real mode default value */
-END(machine_real_restart_idt)
-
-	.balign	16
-GLOBAL(machine_real_restart_gdt)
-	/* Self-pointer */
-	.word	0xffff		/* Length - real mode default value */
-	.long	pa_machine_real_restart_gdt
-	.word	0
-
-	/*
-	 * 16-bit code segment pointing to real_mode_seg
-	 * Selector value 8
-	 */
-	.word	0xffff		/* Limit */
-	.long	0x9b000000 + pa_real_mode_base
-	.word	0
-
-	/*
-	 * 16-bit data segment with the selector value 16 = 0x10 and
-	 * base value 0x100; since this is consistent with real mode
-	 * semantics we don't have to reload the segments once CR0.PE = 0.
-	 */
-	.quad	GDT_ENTRY(0x0093, 0x100, 0xffff)
-END(machine_real_restart_gdt)