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

Praveen Paladugu
2025-11-17T21:11:39Z

On Thu, Nov 13, 2025 at 07:42:00PM +0000, Michael Kelley wrote:
> 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.
>
I re-checked and confirmed this gating is no longer necessary. I dropped
it in v5.

> > > +/*
> > > + * 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