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

7 files changed, 55 insertions, 38 deletions

diff --git a/arch/x86/include/asm/emergency-restart.h b/arch/x86/include/asm/emergency-restart.h
index cc70c1c78ca..75ce3f47d20 100644
--- a/arch/x86/include/asm/emergency-restart.h
+++ b/arch/x86/include/asm/emergency-restart.h
@@ -4,9 +4,7 @@
 enum reboot_type {
         BOOT_TRIPLE = 't',
         BOOT_KBD = 'k',
-#ifdef CONFIG_X86_32
         BOOT_BIOS = 'b',
-#endif
         BOOT_ACPI = 'a',
         BOOT_EFI = 'e',
         BOOT_CF9 = 'p',
diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index fce3f4ae5bd..fe1ec5bcd84 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -21,8 +21,9 @@ struct real_mode_header {
         u32     wakeup_header;
 #endif
         /* APM/BIOS reboot */
-#ifdef CONFIG_X86_32
         u32     machine_real_restart_asm;
+#ifdef CONFIG_X86_64
+        u32     machine_real_restart_seg;
 #endif
 };
 
diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index 92f297069e8..a82c4f1b4d8 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -18,8 +18,8 @@ extern struct machine_ops machine_ops;
 
 void native_machine_crash_shutdown(struct pt_regs *regs);
 void native_machine_shutdown(void);
-void machine_real_restart(unsigned int type);
-/* These must match dispatch_table in reboot_32.S */
+void __noreturn machine_real_restart(unsigned int type);
+/* These must match dispatch in arch/x86/realmore/rm/reboot.S */
 #define MRR_BIOS        0
 #define MRR_APM         1
 
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 25b48edb847..6ddb9cd0ced 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -20,14 +20,12 @@
 #include <asm/virtext.h>
 #include <asm/cpu.h>
 #include <asm/nmi.h>
+#include <asm/smp.h>
 
-#ifdef CONFIG_X86_32
-# include <linux/ctype.h>
-# include <linux/mc146818rtc.h>
-# include <asm/realmode.h>
-#else
-# include <asm/x86_init.h>
-#endif
+#include <linux/ctype.h>
+#include <linux/mc146818rtc.h>
+#include <asm/realmode.h>
+#include <asm/x86_init.h>
 
 /*
  * Power off function, if any
@@ -49,7 +47,7 @@ int reboot_force;
  */
 static int reboot_default = 1;
 
-#if defined(CONFIG_X86_32) && defined(CONFIG_SMP)
+#ifdef CONFIG_SMP
 static int reboot_cpu = -1;
 #endif
 
@@ -67,8 +65,8 @@ bool port_cf9_safe = false;
  * reboot=b[ios] | s[mp] | t[riple] | k[bd] | e[fi] [, [w]arm | [c]old] | p[ci]
  * warm   Don't set the cold reboot flag
  * cold   Set the cold reboot flag
- * bios   Reboot by jumping through the BIOS (only for X86_32)
- * smp    Reboot by executing reset on BSP or other CPU (only for X86_32)
+ * bios   Reboot by jumping through the BIOS
+ * smp    Reboot by executing reset on BSP or other CPU
  * triple Force a triple fault (init)
  * kbd    Use the keyboard controller. cold reset (default)
  * acpi   Use the RESET_REG in the FADT
@@ -95,7 +93,6 @@ static int __init reboot_setup(char *str)
                         reboot_mode = 0;
                         break;
 
-#ifdef CONFIG_X86_32
 #ifdef CONFIG_SMP
                 case 's':
                         if (isdigit(*(str+1))) {
@@ -112,7 +109,6 @@ static int __init reboot_setup(char *str)
 #endif /* CONFIG_SMP */
 
                 case 'b':
-#endif
                 case 'a':
                 case 'k':
                 case 't':
@@ -138,7 +134,6 @@ static int __init reboot_setup(char *str)
 __setup("reboot=", reboot_setup);
 
 
-#ifdef CONFIG_X86_32
 /*
  * Reboot options and system auto-detection code provided by
  * Dell Inc. so their systems "just work". :-)
@@ -157,11 +152,8 @@ static int __init set_bios_reboot(const struct dmi_system_id *d)
         return 0;
 }
 
-void machine_real_restart(unsigned int type)
+void __noreturn machine_real_restart(unsigned int type)
 {
-        void (*restart_lowmem)(unsigned int) = (void (*)(unsigned int))
-                real_mode_header->machine_real_restart_asm;
-
         local_irq_disable();
 
         /*
@@ -181,7 +173,11 @@ void machine_real_restart(unsigned int type)
         /*
          * Switch back to the initial page table.
          */
+#ifdef CONFIG_X86_32
         load_cr3(initial_page_table);
+#else
+        write_cr3(real_mode_header->trampoline_pgd);
+#endif
 
         /*
          * Write 0x1234 to absolute memory location 0x472.  The BIOS reads
@@ -192,14 +188,21 @@ void machine_real_restart(unsigned int type)
         *((unsigned short *)0x472) = reboot_mode;
 
         /* Jump to the identity-mapped low memory code */
-        restart_lowmem(type);
+#ifdef CONFIG_X86_32
+        asm volatile("jmpl *%0" : :
+                     "rm" (real_mode_header->machine_real_restart_asm),
+                     "a" (type));
+#else
+        asm volatile("ljmpl *%0" : :
+                     "m" (real_mode_header->machine_real_restart_asm),
+                     "D" (type));
+#endif
+        unreachable();
 }
 #ifdef CONFIG_APM_MODULE
 EXPORT_SYMBOL(machine_real_restart);
 #endif
 
-#endif /* CONFIG_X86_32 */
-
 /*
  * Some Apple MacBook and MacBookPro's needs reboot=p to be able to reboot
  */
@@ -223,11 +226,9 @@ static int __init set_kbd_reboot(const struct dmi_system_id *d)
 }
 
 /*
- * This is a single dmi_table handling all reboot quirks.  Note that
- * REBOOT_BIOS is only available for 32bit
+ * This is a single dmi_table handling all reboot quirks.
  */
 static struct dmi_system_id __initdata reboot_dmi_table[] = {
-#ifdef CONFIG_X86_32
         {       /* Handle problems with rebooting on Dell E520's */
                 .callback = set_bios_reboot,
                 .ident = "Dell E520",
@@ -377,7 +378,6 @@ static struct dmi_system_id __initdata reboot_dmi_table[] = {
                         DMI_MATCH(DMI_BOARD_NAME, "P4S800"),
                 },
         },
-#endif /* CONFIG_X86_32 */
 
         {       /* Handle reboot issue on Acer Aspire one */
                 .callback = set_kbd_reboot,
@@ -576,13 +576,11 @@ static void native_machine_emergency_restart(void)
                         reboot_type = BOOT_KBD;
                         break;
 
-#ifdef CONFIG_X86_32
                 case BOOT_BIOS:
                         machine_real_restart(MRR_BIOS);
 
                         reboot_type = BOOT_KBD;
                         break;
-#endif
 
                 case BOOT_ACPI:
                         acpi_reboot();
@@ -624,12 +622,10 @@ void native_machine_shutdown(void)
         /* The boot cpu is always logical cpu 0 */
         int reboot_cpu_id = 0;
 
-#ifdef CONFIG_X86_32
         /* See if there has been given a command line override */
         if ((reboot_cpu != -1) && (reboot_cpu < nr_cpu_ids) &&
                 cpu_online(reboot_cpu))
                 reboot_cpu_id = reboot_cpu;
-#endif
 
         /* Make certain the cpu I'm about to reboot on is online */
         if (!cpu_online(reboot_cpu_id))
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index 5b84a2d3088..b2d534cab25 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -22,7 +22,7 @@ wakeup-objs	+= video-bios.o
 realmode-y                      += header.o
 realmode-y                      += trampoline_$(BITS).o
 realmode-y                      += stack.o
-realmode-$(CONFIG_X86_32)       += reboot_32.o
+realmode-y                      += reboot.o
 realmode-$(CONFIG_ACPI_SLEEP)   += $(wakeup-objs)
 
 targets += $(realmode-y)
diff --git a/arch/x86/realmode/rm/header.S b/arch/x86/realmode/rm/header.S
index fadf48378ad..a28221d94e6 100644
--- a/arch/x86/realmode/rm/header.S
+++ b/arch/x86/realmode/rm/header.S
@@ -6,6 +6,7 @@
 
 #include <linux/linkage.h>
 #include <asm/page_types.h>
+#include <asm/segment.h>
 
 #include "realmode.h"
         
@@ -28,8 +29,9 @@ GLOBAL(real_mode_header)
         .long   pa_wakeup_header
 #endif
         /* APM/BIOS reboot */
-#ifdef CONFIG_X86_32
         .long   pa_machine_real_restart_asm
+#ifdef CONFIG_X86_64
+        .long   __KERNEL32_CS
 #endif
 END(real_mode_header)
 
diff --git a/arch/x86/realmode/rm/reboot_32.S b/arch/x86/realmode/rm/reboot.S
index 114044876b3..6bf8feac555 100644
--- a/arch/x86/realmode/rm/reboot_32.S
+++ b/arch/x86/realmode/rm/reboot.S
@@ -2,6 +2,8 @@
 #include <linux/init.h>
 #include <asm/segment.h>
 #include <asm/page_types.h>
+#include <asm/processor-flags.h>
+#include <asm/msr-index.h>
 #include "realmode.h"
 
 /*
@@ -12,13 +14,31 @@
  * 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.
+ * This code is called with the restart type (0 = BIOS, 1 = APM) in
+ * the primary argument register (%eax for 32 bit, %edi for 64 bit).
  */
         .section ".text32", "ax"
         .code32
-
-        .balign 16
 ENTRY(machine_real_restart_asm)
+
+#ifdef CONFIG_X86_64
+
+        /* Disable paging to drop us out of long mode */
+        movl    %cr0, %eax
+        andl    $~X86_CR0_PG, %eax
+        movl    %eax, %cr0
+        jmp     1f      /* "A branch" may be needed here, assume near is OK */
+
+1:
+        xorl    %eax, %eax
+        xorl    %edx, %edx
+        movl    $MSR_EFER, %ecx
+        wrmsr
+
+        movl    %edi, %eax
+        
+#endif /* CONFIG_X86_64 */
+        
         /* Set up the IDT for real mode. */
         lidtl   pa_machine_real_restart_idt