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

Michael Kelley
2025-11-13T19:42:03Z

From: Praveen K Paladugu <prapal@linux.microsoft.com> Sent: Friday, November 7, 2025 2:25 PM
>
> 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)

Is gating on CONFIG_ACPI necessary? I thought this might be leftover from earlier
versions when you were calling acpi_os_set_prepare_sleep() and
acpi_os_set_prepare_extended_sleep(). In my testing, this current version
compiles OK if the gating is removed and CONFIG_ACPI=n, as the ACPI functions
you are calling have stubs in that case.

> > +/*
> > + * 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