[PATCH v3] x86: hyperv: fix build in !CONFIG_KEXEC_CORE case

[Vitaly Kuznetsov]

Recent changes in Hyper-V driver ("Drivers: hv: vmbus: add special crash
handler") broke the build when CONFIG_KEXEC_CORE is not set:

arch/x86/built-in.o: In function `hv_machine_crash_shutdown':
arch/x86/kernel/cpu/mshyperv.c:112: undefined reference to `native_machine_crash_shutdown'

Decorate all kexec related code with #ifdef CONFIG_KEXEC_CORE.

Reported-by: Jim Davis <jim.epost@xxxxxxxxx>
Reported-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
Changes since v2:
- Hide hv_kexec_handler/hv_crash_handler under IS_ENABLED(CONFIG_HYPERV)
  to avoid warings in !CONFIG_HYPERV && !CONFIG_KEXEC case [kbuild robot]

Changes since v1:
- Previously I tried solving the issue by defining
  native_machine_crash_shutdown in !CONFIG_KEXEC_CORE case:
  https://lkml.org/lkml/2015/8/11/417. This was to   avoid having #ifdefs
  in C code [Greg KH]. Such approach, however, raised a question on
  bloating kernel with unneeded stuff [Ingo Molnar].
---
 arch/x86/kernel/cpu/mshyperv.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 381c8b9..20e242e 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -34,11 +34,10 @@
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
 
-static void (*hv_kexec_handler)(void);
-static void (*hv_crash_handler)(struct pt_regs *regs);
-
 #if IS_ENABLED(CONFIG_HYPERV)
 static void (*vmbus_handler)(void);
+static void (*hv_kexec_handler)(void);
+static void (*hv_crash_handler)(struct pt_regs *regs);
 
 void hyperv_vector_handler(struct pt_regs *regs)
 {
@@ -96,8 +95,8 @@ void hv_remove_crash_handler(void)
 	hv_crash_handler = NULL;
 }
 EXPORT_SYMBOL_GPL(hv_remove_crash_handler);
-#endif
 
+#ifdef CONFIG_KEXEC_CORE
 static void hv_machine_shutdown(void)
 {
 	if (kexec_in_progress && hv_kexec_handler)
@@ -111,7 +110,8 @@ static void hv_machine_crash_shutdown(struct pt_regs *regs)
 		hv_crash_handler(regs);
 	native_machine_crash_shutdown(regs);
 }
-
+#endif /* CONFIG_KEXEC_CORE */
+#endif /* CONFIG_HYPERV */
 
 static uint32_t  __init ms_hyperv_platform(void)
 {
@@ -186,8 +186,10 @@ static void __init ms_hyperv_init_platform(void)
 	no_timer_check = 1;
 #endif
 
+#if IS_ENABLED(CONFIG_HYPERV) && defined(CONFIG_KEXEC_CORE)
 	machine_ops.shutdown = hv_machine_shutdown;
 	machine_ops.crash_shutdown = hv_machine_crash_shutdown;
+#endif
 	mark_tsc_unstable("running on Hyper-V");
 }
 
-- 
2.4.3

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