x86/shutdown: Support for using SCHEDOP_{shutdown,reboot}

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

docs/misc/xen-command-line.markdown

@@ -1506,6 +1506,9 @@ Specify the host reboot method.
 'efi' instructs Xen to reboot using the EFI reboot call (in EFI mode by
  default it will use that method first).
 
+`xen` instructs Xen to reboot using Xen's SCHEDOP hypercall (this is the default
+when running nested Xen)
+
 ### rmrr
 > '= start<-end>=[s1]bdf1[,[s1]bdf2[,...]];start<-end>=[s2]bdf1[,[s2]bdf2[,...]]
 

xen/arch/x86/shutdown.c

@@ -25,6 +25,7 @@
 #include <asm/mpspec.h>
 #include <asm/tboot.h>
 #include <asm/apic.h>
+#include <asm/guest.h>
 
 enum reboot_type {
         BOOT_INVALID,
@@ -34,6 +35,7 @@ enum reboot_type {
         BOOT_CF9 = 'p',
         BOOT_CF9_PWR = 'P',
         BOOT_EFI = 'e',
+        BOOT_XEN = 'x',
 };
 
 static int reboot_mode;
@@ -49,6 +51,7 @@ static int reboot_mode;
  * pci    Use the so-called "PCI reset register", CF9
  * Power  Like 'pci' but for a full power-cyle reset
  * efi    Use the EFI reboot (if running under EFI)
+ * xen    Use Xen SCHEDOP hypercall (if running under Xen as a guest)
  */
 static enum reboot_type reboot_type = BOOT_INVALID;
 
@@ -75,6 +78,7 @@ static int __init set_reboot_type(const char *str)
         case 'P':
         case 'p':
         case 't':
+        case 'x':
             reboot_type = *str;
             break;
         default:
@@ -93,6 +97,13 @@ static int __init set_reboot_type(const char *str)
         reboot_type = BOOT_INVALID;
     }
 
+    if ( reboot_type == BOOT_XEN && !xen_guest )
+    {
+        printk("Xen reboot selected, but Xen hypervisor not detected\n"
+               "Falling back to default\n");
+        reboot_type = BOOT_INVALID;
+    }
+
     return rc;
 }
 custom_param("reboot", set_reboot_type);
@@ -109,6 +120,10 @@ static inline void kb_wait(void)
 static void noreturn __machine_halt(void *unused)
 {
     local_irq_disable();
+
+    if ( reboot_type == BOOT_XEN )
+        xen_hypercall_shutdown(SHUTDOWN_poweroff);
+
     for ( ; ; )
         halt();
 }
@@ -129,10 +144,17 @@ void machine_halt(void)
 
 static void default_reboot_type(void)
 {
-    if ( reboot_type == BOOT_INVALID )
-        reboot_type = efi_enabled(EFI_RS) ? BOOT_EFI
-                                  : acpi_disabled ? BOOT_KBD
-                                                  : BOOT_ACPI;
+    if ( reboot_type != BOOT_INVALID )
+        return;
+
+    if ( xen_guest )
+        reboot_type = BOOT_XEN;
+    else if ( efi_enabled(EFI_RS) )
+        reboot_type = BOOT_EFI;
+    else if ( acpi_disabled )
+        reboot_type = BOOT_KBD;
+    else
+        reboot_type = BOOT_ACPI;
 }
 
 static int __init override_reboot(struct dmi_system_id *d)
@@ -618,6 +640,10 @@ void machine_restart(unsigned int delay_millisecs)
             }
             reboot_type = BOOT_ACPI;
             break;
+
+        case BOOT_XEN:
+            xen_hypercall_shutdown(SHUTDOWN_reboot);
+            break;
         }
     }
 }

xen/include/asm-x86/guest/hypercall.h

@@ -21,6 +21,11 @@
 
 #ifdef CONFIG_XEN_GUEST
 
+#include <xen/types.h>
+
+#include <public/xen.h>
+#include <public/sched.h>
+
 /*
  * Hypercall primatives for 64bit
  *
@@ -78,6 +83,33 @@
         (type)res;                                                      \
     })
 
+/*
+ * Primitive Hypercall wrappers
+ */
+static inline long xen_hypercall_sched_op(unsigned int cmd, void *arg)
+{
+    return _hypercall64_2(long, __HYPERVISOR_sched_op, cmd, arg);
+}
+
+/*
+ * Higher level hypercall helpers
+ */
+static inline long xen_hypercall_shutdown(unsigned int reason)
+{
+    struct sched_shutdown s = { .reason = reason };
+    return xen_hypercall_sched_op(SCHEDOP_shutdown, &s);
+}
+
+#else /* CONFIG_XEN_GUEST */
+
+#include <public/sched.h>
+
+static inline long xen_hypercall_shutdown(unsigned int reason)
+{
+    ASSERT_UNREACHABLE();
+    return 0;
+}
+
 #endif /* CONFIG_XEN_GUEST */
 #endif /* __X86_XEN_HYPERCALL_H__ */