RE: [PATCH v4 1/3] hyperv: Add definitions for MSHV sleep state configuration

Michael Kelley
2025-11-13T19:42:00Z

From: Praveen K Paladugu <prapal@linux.microsoft.com> Sent: Friday, November 7, 2025 2:17 PM
>
> Add the definitions required to configure sleep states in mshv hypervsior.
>
> 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>
> Reviewed-by: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>
> Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> ---
> include/hyperv/hvgdk_mini.h | 4 +++-
> include/hyperv/hvhdk_mini.h | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> index 7499a679e60a..b43fa1c9ed2c 100644
> --- a/include/hyperv/hvgdk_mini.h
> +++ b/include/hyperv/hvgdk_mini.h
> @@ -465,19 +465,21 @@ union hv_vp_assist_msr_contents { /*
> HV_REGISTER_VP_ASSIST_PAGE */
> #define HVCALL_RESET_DEBUG_SESSION 0x006b
> #define HVCALL_MAP_STATS_PAGE 0x006c
> #define HVCALL_UNMAP_STATS_PAGE 0x006d
> +#define HVCALL_SET_SYSTEM_PROPERTY 0x006f
> #define HVCALL_ADD_LOGICAL_PROCESSOR 0x0076
> #define HVCALL_GET_SYSTEM_PROPERTY 0x007b
> #define HVCALL_MAP_DEVICE_INTERRUPT 0x007c
> #define HVCALL_UNMAP_DEVICE_INTERRUPT 0x007d
> #define HVCALL_RETARGET_INTERRUPT 0x007e
> #define HVCALL_NOTIFY_PARTITION_EVENT 0x0087
> +#define HVCALL_ENTER_SLEEP_STATE 0x0084
> #define HVCALL_NOTIFY_PORT_RING_EMPTY 0x008b
> #define HVCALL_REGISTER_INTERCEPT_RESULT 0x0091
> #define HVCALL_ASSERT_VIRTUAL_INTERRUPT 0x0094
> #define HVCALL_CREATE_PORT 0x0095
> #define HVCALL_CONNECT_PORT 0x0096
> #define HVCALL_START_VP 0x0099
> -#define HVCALL_GET_VP_INDEX_FROM_APIC_ID 0x009a
> +#define HVCALL_GET_VP_INDEX_FROM_APIC_ID 0x009a
> #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
> #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
> #define HVCALL_SIGNAL_EVENT_DIRECT 0x00c0
> diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
> index f2d7b50de7a4..06cf30deb319 100644
> --- a/include/hyperv/hvhdk_mini.h
> +++ b/include/hyperv/hvhdk_mini.h
> @@ -140,6 +140,7 @@ enum hv_snp_status {
>
> enum hv_system_property {
> /* Add more values when needed */
> + HV_SYSTEM_PROPERTY_SLEEP_STATE = 3,
> HV_SYSTEM_PROPERTY_SCHEDULER_TYPE = 15,
> HV_DYNAMIC_PROCESSOR_FEATURE_PROPERTY = 21,
> HV_SYSTEM_PROPERTY_CRASHDUMPAREA = 47,
> @@ -155,6 +156,19 @@ union hv_pfn_range { /* HV_SPA_PAGE_RANGE */
> } __packed;
> };
>
> +enum hv_sleep_state {
> + HV_SLEEP_STATE_S1 = 1,
> + HV_SLEEP_STATE_S2 = 2,
> + HV_SLEEP_STATE_S3 = 3,
> + HV_SLEEP_STATE_S4 = 4,
> + HV_SLEEP_STATE_S5 = 5,
> + /*
> + * After hypervisor has received this, any follow up sleep
> + * state registration requests will be rejected.
> + */
> + HV_SLEEP_STATE_LOCK = 6
> +};
> +
> enum hv_dynamic_processor_feature_property {
> /* Add more values when needed */
> HV_X64_DYNAMIC_PROCESSOR_FEATURE_MAX_ENCRYPTED_PARTITIONS =
> 13,
> @@ -184,6 +198,25 @@ struct hv_output_get_system_property {
> };
> } __packed;
>
> +struct hv_sleep_state_info {
> + u32 sleep_state; /* enum hv_sleep_state */
> + u8 pm1a_slp_typ;
> + u8 pm1b_slp_typ;
> +} __packed;
> +
> +struct hv_input_set_system_property {
> + u32 property_id; /* enum hv_system_property */
> + u32 reserved;
> + union {
> + /* More fields to be filled in when needed */
> + struct hv_sleep_state_info set_sleep_state_info;
> + };
> +} __packed;

Because struct hv_sleep_state_info is 6 bytes long, this
hypercall input struct ends up being 14 bytes long, which is
unusual. Hyper-V almost always makes hypercall input size
a multiple of 8 bytes, though in a few cases the last 4 bytes
might be ignored, making it a multiple of 4 bytes. So I'm
wondering if there should be a 2 byte "reserved" field in
struct hv_sleep_state_info so that everything ends up
being a multiple of 8 bytes.

Since there aren't any fields after such a putative "reserved"
field, there's nothing currently at the wrong offset. But it would
affect how much space gets zero'ed in hv_initialize_sleep_states().
Zero'ing those last 2 bytes might prove useful if future versions
of the hypervisor were to use those 2 bytes for an additional
field or two.

> +
> +struct hv_input_enter_sleep_state { /* HV_INPUT_ENTER_SLEEP_STATE */
> + u32 sleep_state; /* enum hv_sleep_state */
> +} __packed;
> +
> struct hv_input_map_stats_page {
> u32 type; /* enum hv_stats_object_type */
> u32 padding;
> --
> 2.51.0