[PATCH v2 2/2] hyperv: Enable clean shutdown for root partition with MSHV

[Praveen K Paladugu <prapal@linux.microsoft.com>]

When a shutdown is initiated in the root partition without configuring
sleep states, the call to `hv_call_enter_sleep_state` fails. In such cases
the root falls back to using legacy ACPI mechanisms to poweroff. This call
is intercepted by MSHV and will result in a Machine Check Exception (MCE).

Root 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 prevent this, properly configure sleep states within MSHV, allowing
the root partition to shut down cleanly without triggering a panic.

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       |   7 ++
 arch/x86/include/asm/mshyperv.h |   1 +
 drivers/hv/hv_common.c          | 119 ++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index afdbda2dd7b7..57bd96671ead 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -510,6 +510,13 @@ void __init hyperv_init(void)
 		memunmap(src);
 
 		hv_remap_tsc_clocksource();
+		/*
+		 * The notifier registration might fail at various hops.
+		 * Corresponding error messages will land in dmesg. There is
+		 * otherwise nothing that can be specifically done to handle
+		 * failures here.
+		 */
+		(void)hv_sleep_notifiers_register();
 	} 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 abc4659f5809..fb8d691193df 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -236,6 +236,7 @@ int hyperv_fill_flush_guest_mapping_list(
 void hv_apic_init(void);
 void __init hv_init_spinlocks(void);
 bool hv_vcpu_is_preempted(int vcpu);
+int hv_sleep_notifiers_register(void);
 #else
 static inline void hv_apic_init(void) {}
 #endif
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index e109a620c83f..cfba9ded7bcb 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -837,3 +837,122 @@ const char *hv_result_to_string(u64 status)
 	return "Unknown";
 }
 EXPORT_SYMBOL_GPL(hv_result_to_string);
+
+#if IS_ENABLED(CONFIG_ACPI)
+/*
+ * Corresponding sleep states have to be initialized in order for a subsequent
+ * HVCALL_ENTER_SLEEP_STATE call to succeed. Currently only S5 state as per
+ * ACPI 6.4 chapter 7.4.2 is relevant, while S1, S2 and S3 can be supported.
+ *
+ * ACPI should be initialized and should support S5 sleep state when this method
+ * is called, so that it can extract correct PM values and pass them to hv.
+ */
+static int hv_initialize_sleep_states(void)
+{
+	u64 status;
+	unsigned long flags;
+	struct hv_input_set_system_property *in;
+	acpi_status acpi_status;
+	u8 sleep_type_a, sleep_type_b;
+
+	if (!acpi_sleep_state_supported(ACPI_STATE_S5)) {
+		pr_err("%s: S5 sleep state not supported.\n", __func__);
+		return -ENODEV;
+	}
+
+	acpi_status = acpi_get_sleep_type_data(ACPI_STATE_S5,
+						&sleep_type_a, &sleep_type_b);
+	if (ACPI_FAILURE(acpi_status))
+		return -ENODEV;
+
+	local_irq_save(flags);
+	in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(in, 0, sizeof(*in));
+
+	in->property_id = HV_SYSTEM_PROPERTY_SLEEP_STATE;
+	in->set_sleep_state_info.sleep_state = HV_SLEEP_STATE_S5;
+	in->set_sleep_state_info.pm1a_slp_typ = sleep_type_a;
+	in->set_sleep_state_info.pm1b_slp_typ = sleep_type_b;
+
+	status = hv_do_hypercall(HVCALL_SET_SYSTEM_PROPERTY, in, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status)) {
+		hv_status_err(status, "\n");
+		return hv_result_to_errno(status);
+	}
+
+	return 0;
+}
+
+static int hv_call_enter_sleep_state(u32 sleep_state)
+{
+	u64 status;
+	int ret;
+	unsigned long flags;
+	struct hv_input_enter_sleep_state *in;
+
+	ret = hv_initialize_sleep_states();
+	if (ret)
+		return ret;
+
+	local_irq_save(flags);
+	in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	in->sleep_state = sleep_state;
+
+	status = hv_do_hypercall(HVCALL_ENTER_SLEEP_STATE, in, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status)) {
+		hv_status_err(status, "\n");
+		return hv_result_to_errno(status);
+	}
+
+	return 0;
+}
+
+static int hv_reboot_notifier_handler(struct notifier_block *this,
+				      unsigned long code, void *another)
+{
+	int ret = 0;
+
+	if (code == SYS_HALT || code == SYS_POWER_OFF)
+		ret = hv_call_enter_sleep_state(HV_SLEEP_STATE_S5);
+
+	return ret ? NOTIFY_DONE : NOTIFY_OK;
+}
+
+static struct notifier_block hv_reboot_notifier = {
+	.notifier_call  = hv_reboot_notifier_handler,
+};
+
+static int hv_acpi_sleep_handler(u8 sleep_state, u32 pm1a_cnt, u32 pm1b_cnt)
+{
+	int ret = 0;
+
+	if (sleep_state == ACPI_STATE_S5)
+		ret = hv_call_enter_sleep_state(HV_SLEEP_STATE_S5);
+
+	return ret == 0 ? 1 : -1;
+}
+
+static int hv_acpi_extended_sleep_handler(u8 sleep_state, u32 val_a, u32 val_b)
+{
+	return hv_acpi_sleep_handler(sleep_state, val_a, val_b);
+}
+
+int hv_sleep_notifiers_register(void)
+{
+	int ret;
+
+	acpi_os_set_prepare_sleep(&hv_acpi_sleep_handler);
+	acpi_os_set_prepare_extended_sleep(&hv_acpi_extended_sleep_handler);
+
+	ret = register_reboot_notifier(&hv_reboot_notifier);
+	if (ret)
+		pr_err("%s: cannot register reboot notifier %d\n",
+			__func__, ret);
+
+	return ret;
+}
+#endif
-- 
2.51.0