linux-kernel - [PATCH v4 3/3] hyperv: Cleanly shutdown root partition with MSHV

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Message-ID: <20251107221700.45957-4-prapal@linux.microsoft.com>
Date: Fri,  7 Nov 2025 16:16:49 -0600
From: Praveen K Paladugu <prapal@...ux.microsoft.com>
To: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	tglx@...utronix.de,
	mingo@...hat.com,
	linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	hpa@...or.com,
	arnd@...db.de
Cc: anbelski@...ux.microsoft.com,
	prapal@...ux.microsoft.com,
	easwar.hariharan@...ux.microsoft.com,
	nunodasneves@...ux.microsoft.com,
	skinsburskii@...ux.microsoft.com,
	mhklinux@...look.com
Subject: [PATCH v4 3/3] hyperv: Cleanly shutdown root partition with MSHV

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@...ux.microsoft.com>
Co-developed-by: Anatol Belski <anbelski@...ux.microsoft.com>
Signed-off-by: Anatol Belski <anbelski@...ux.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