Re: [PATCH v4 2/3] hyperv: Use reboot notifier to configure sleep state

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

On 11/7/2025 4:16 PM, Praveen K Paladugu wrote:
> Configure sleep state information in mshv hypervisor. This sleep state
> information from ACPI will be used by hypervisor to poweroff the host.
> 
> 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 |  2 +
>   drivers/hv/mshv_common.c        | 80 +++++++++++++++++++++++++++++++++
>   3 files changed, 89 insertions(+)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index e28737ec7054..645b52dd732e 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -555,6 +555,13 @@ void __init hyperv_init(void)
>   
>   		hv_remap_tsc_clocksource();
>   		hv_root_crash_init();
> +		/*
> +		 * 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.
> +		 */
> +		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 1342d55c2545..fbc1233175ce 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -181,8 +181,10 @@ 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);
> +void hv_sleep_notifiers_register(void);
>   #else
>   static inline void hv_apic_init(void) {}
> +static inline void hv_sleep_notifiers_register(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 aa2be51979fd..d1a1daa52b65 100644
> --- a/drivers/hv/mshv_common.c
> +++ b/drivers/hv/mshv_common.c
> @@ -14,6 +14,9 @@
>   #include <asm/mshyperv.h>
>   #include <linux/resume_user_mode.h>
>   #include <linux/export.h>
> +#include <linux/acpi.h>
> +#include <linux/notifier.h>
> +#include <linux/reboot.h>
>   
>   #include "mshv.h"
>   
> @@ -138,3 +141,80 @@ int hv_call_get_partition_property(u64 partition_id,
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(hv_call_get_partition_property);
> +
> +#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.
> + *
> + * In order to pass proper PM values to mshv, ACPI should be initialized and
> + * should support S5 sleep state when this method is invoked.
> + */
> +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;
> +}
> +
> +/*
> + * This notifier initializes sleep states in mshv hypervisor which will be
> + * used during power off.
> + */
> +static int hv_reboot_notifier_handler(struct notifier_block *this,
> +				      unsigned long code, void *another)
> +{
> +	int ret = 0;
> +
> +	if (code == SYS_POWER_OFF)

This patchset only addresses poweroff.
Reboot currently works via ACPI. Nothing more is needed there.

`kernel_halt` needs the use of a different hypercall. Support for
Halting will be introduced later.
> +		ret = hv_initialize_sleep_states();
> +
> +	return ret ? NOTIFY_DONE : NOTIFY_OK;
> +}
> +
> +static struct notifier_block hv_reboot_notifier = {
> +	.notifier_call = hv_reboot_notifier_handler,
> +};
> +
> +void hv_sleep_notifiers_register(void)
> +{
> +	int ret;
> +
> +	ret = register_reboot_notifier(&hv_reboot_notifier);
> +	if (ret)
> +		pr_err("%s: cannot register reboot notifier %d\n", __func__,
> +		       ret);
> +}
> +#endif