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

Praveen K Paladugu
2025-11-07T22:17:16Z

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