When a root partition running on MSHV is powered off, the default
behavior is to write ACPI registers to power-off. However, this ACPI
write is intercepted by MSHV and will result in a Machine Check
Exception(MCE).

The root partition eventually panics with a trace similar to:

  [   81.306348] reboot: Power down
  [   81.314709] mce: [Hardware Error]: CPU 0: Machine Check Exception: 4 Bank 0: b2000000c0060001
  [   81.314711] mce: [Hardware Error]: TSC 3b8cb60a66 PPIN 11d98332458e4ea9
  [   81.314713] mce: [Hardware Error]: PROCESSOR 0:606a6 TIME 1759339405 SOCKET 0 APIC 0 microcode ffffffff
  [   81.314715] mce: [Hardware Error]: Run the above through 'mcelog --ascii'
  [   81.314716] mce: [Hardware Error]: Machine check: Processor context corrupt
  [   81.314717] Kernel panic - not syncing: Fatal machine check

To correctly shutdown a root partition running on MSHV, sleep state
information has be configured within mshv. Later HVCALL_ENTER_SLEEP_STATE
should be invoked as the last step in the shutdown sequence.

The previous patch configures the sleep state information and this patch
invokes HVCALL_ENTER_SLEEP_STATE to cleanly shutdown the root partition.

Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>
Co-developed-by: Anatol Belski <anbelski@linux.microsoft.com>
Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
---
 arch/x86/hyperv/hv_init.c       |  2 ++
 arch/x86/include/asm/mshyperv.h |  2 ++
 drivers/hv/mshv_common.c        | 19 +++++++++++++++++++
 3 files changed, 23 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 645b52dd732e..24824534ff8d 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -34,6 +34,7 @@
 #include <clocksource/hyperv_timer.h>
 #include <linux/highmem.h>
 #include <linux/export.h>
+#include <asm/reboot.h>
 
 void *hv_hypercall_pg;
 
@@ -562,6 +563,7 @@ void __init hyperv_init(void)
 		 * failures here.
 		 */
 		hv_sleep_notifiers_register();
+		machine_ops.power_off = hv_machine_power_off;
 	} else {
 		hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
 		wrmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index fbc1233175ce..9082d56103ce 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -182,9 +182,11 @@ void hv_apic_init(void);
 void __init hv_init_spinlocks(void);
 bool hv_vcpu_is_preempted(int vcpu);
 void hv_sleep_notifiers_register(void);
+void hv_machine_power_off(void);
 #else
 static inline void hv_apic_init(void) {}
 static inline void hv_sleep_notifiers_register(void) {};
+static inline void hv_machine_power_off(void) {};
 #endif
 
 struct irq_domain *hv_create_pci_msi_domain(void);
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index d1a1daa52b65..0588d293a92a 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -217,4 +217,23 @@ void hv_sleep_notifiers_register(void)
 		pr_err("%s: cannot register reboot notifier %d\n", __func__,
 		       ret);
 }
+
+/*
+ * Power off the machine by entering S5 sleep state via Hyper-V hypercall.
+ * This call does not return if successful.
+ */
+void hv_machine_power_off(void)
+{
+	u64 status;
+	unsigned long flags;
+	struct hv_input_enter_sleep_state *in;
+
+	local_irq_save(flags);
+	in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	in->sleep_state = HV_SLEEP_STATE_S5;
+
+	status = hv_do_hypercall(HVCALL_ENTER_SLEEP_STATE, in, NULL);
+	local_irq_restore(flags);
+
+}
 #endif
-- 
2.51.0

Hi Praveen,

kernel test robot noticed the following build warnings:

[auto build test WARNING on next-20251107]
[cannot apply to tip/x86/core linus/master v6.18-rc4 v6.18-rc3 v6.18-rc2 v6.18-rc4]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Praveen-K-Paladugu/hyperv-Add-definitions-for-MSHV-sleep-state-configuration/20251108-061825
base:   next-20251107
patch link:    https://lore.kernel.org/r/20251107221700.45957-4-prapal%40linux.microsoft.com
patch subject: [PATCH v4 3/3] hyperv: Cleanly shutdown root partition with MSHV
config: x86_64-randconfig-122-20251108 (https://download.01.org/0day-ci/archive/20251108/202511082249.JoKyyEEZ-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251108/202511082249.JoKyyEEZ-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511082249.JoKyyEEZ-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/hv/mshv_common.c:227:6: warning: variable 'status' set but not used [-Wunused-but-set-variable]
     227 |         u64 status;
         |             ^
   1 warning generated.


vim +/status +227 drivers/hv/mshv_common.c

   220	
   221	/*
   222	 * Power off the machine by entering S5 sleep state via Hyper-V hypercall.
   223	 * This call does not return if successful.
   224	 */
   225	void hv_machine_power_off(void)
   226	{
 > 227		u64 status;
   228		unsigned long flags;
   229		struct hv_input_enter_sleep_state *in;
   230	
   231		local_irq_save(flags);
   232		in = *this_cpu_ptr(hyperv_pcpu_input_arg);
   233		in->sleep_state = HV_SLEEP_STATE_S5;
   234	
   235		status = hv_do_hypercall(HVCALL_ENTER_SLEEP_STATE, in, NULL);
   236		local_irq_restore(flags);
   237	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki