Re: [PATCH v3 1/5] hyperv: Introduce new hypercall interfaces used by Hyper-V guest IOMMU

From: Jacob Pan

Date: Wed Aug 12 2026 - 14:10:32 EST

Hi Yu,

On Tue, 11 Aug 2026 23:50:17 +0800
Yu Zhang <zhangyu1@xxxxxxxxxxxxxxxxxxx> wrote:

> From: Wei Liu <wei.liu@xxxxxxxxxx>
>
> Hyper-V guest IOMMU is a para-virtualized IOMMU based on hypercalls.
> Introduce the hypercalls used by the child partition to interact with
> this facility.
>
> These hypercalls fall into below categories:
> - Detection and capability: HVCALL_GET_IOMMU_CAPABILITIES is used to
> detect the existence and capabilities of the guest IOMMU.
>
> - Device management: HVCALL_GET_LOGICAL_DEVICE_PROPERTY is used to
> check whether an endpoint device is managed by the guest IOMMU.
>
> - Domain management: A set of hypercalls is provided to handle the
> creation, configuration, and deletion of guest domains, as well as
> the attachment/detachment of endpoint devices to/from those domains.
>
> - IOTLB flushing: HVCALL_FLUSH_DEVICE_DOMAIN is used to ask Hyper-V
> for a domain-selective IOTLB flush (which in its handler may flush
> the device TLB as well).
>
> Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
> Co-developed-by: Easwar Hariharan
> <easwar.hariharan@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Easwar
> Hariharan <easwar.hariharan@xxxxxxxxxxxxxxxxxxx> Co-developed-by: Yu
> Zhang <zhangyu1@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Yu Zhang
> <zhangyu1@xxxxxxxxxxxxxxxxxxx> ---
> include/hyperv/hvgdk_mini.h | 8 +++
> include/hyperv/hvhdk_mini.h | 126
> ++++++++++++++++++++++++++++++++++++ 2 files changed, 134
> insertions(+)
>
> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> index 6a4e8b9d570f..5bdbb44da112 100644
> --- a/include/hyperv/hvgdk_mini.h
> +++ b/include/hyperv/hvgdk_mini.h
> @@ -486,10 +486,16 @@ union hv_vp_assist_msr_contents { /*
> HV_REGISTER_VP_ASSIST_PAGE */ #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_CREATE_DEVICE_DOMAIN 0x00b1 +#define
> HVCALL_ATTACH_DEVICE_DOMAIN 0x00b2 #define
> HVCALL_SIGNAL_EVENT_DIRECT 0x00c0 #define
> HVCALL_POST_MESSAGE_DIRECT 0x00c1 #define
> HVCALL_DISPATCH_VP 0x00c2 +#define
> HVCALL_DETACH_DEVICE_DOMAIN 0x00c4 +#define
> HVCALL_DELETE_DEVICE_DOMAIN 0x00c5 #define
> HVCALL_GET_GPA_PAGES_ACCESS_STATES 0x00c9 +#define
> HVCALL_CONFIGURE_DEVICE_DOMAIN 0x00ce +#define
> HVCALL_FLUSH_DEVICE_DOMAIN 0x00d0 #define
> HVCALL_ACQUIRE_SPARSE_SPA_PAGE_HOST_ACCESS 0x00d7 #define
> HVCALL_RELEASE_SPARSE_SPA_PAGE_HOST_ACCESS 0x00d8 #define
> HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY 0x00db @@ -502,6
> +508,8 @@ union hv_vp_assist_msr_contents { /*
> HV_REGISTER_VP_ASSIST_PAGE */ #define HVCALL_MMIO_READ
> 0x0106 #define HVCALL_MMIO_WRITE
> 0x0107 #define HVCALL_DISABLE_HYP_EX
> 0x010f +#define HVCALL_GET_IOMMU_CAPABILITIES
> 0x0125 +#define HVCALL_GET_LOGICAL_DEVICE_PROPERTY
> 0x0127 #define HVCALL_MAP_STATS_PAGE2
> 0x0131 /* HV_HYPERCALL_INPUT */
> diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
> index 035ba20870f7..1e3eac99886a 100644
> --- a/include/hyperv/hvhdk_mini.h
> +++ b/include/hyperv/hvhdk_mini.h
> @@ -548,4 +548,130 @@ union hv_device_id { /*
> HV_DEVICE_ID */ } acpi;
> } __packed;
>
> +/* Device domain types */
> +#define HV_DEVICE_DOMAIN_TYPE_S1 1 /* Stage 1 domain */
> +
> +/* ID for default domain and NULL domain */
> +#define HV_DEVICE_DOMAIN_ID_DEFAULT 0
> +#define HV_DEVICE_DOMAIN_ID_NULL 0xFFFFFFFFULL
> +
> +union hv_device_domain_id {
> + u64 as_uint64;
> + struct {
> + u32 type: 4;
> + u32 reserved: 28;
> + u32 id;
> + } __packed;
> +};
> +
> +struct hv_input_device_domain {
> + u64 partition_id;
> + union hv_input_vtl owner_vtl;
> + u8 padding[7];
> + union hv_device_domain_id domain_id;
> +} __packed;
> +
> +union hv_create_device_domain_flags {
> + u32 as_uint32;
> + struct {
> + u32 forward_progress_required: 1;
> + u32 inherit_owning_vtl: 1;
> + u32 reserved: 30;
> + } __packed;
> +};
> +
> +struct hv_input_create_device_domain {
> + struct hv_input_device_domain device_domain;
> + union hv_create_device_domain_flags
> create_device_domain_flags;
> + u32 padding;
> +} __packed;
> +static_assert(sizeof(struct hv_input_create_device_domain) == 32);
nit, maybe also this to detect ABI drift within. Optional.
static_assert(offsetof(struct hv_input_create_device_domain, padding)
== 28);

> +struct hv_input_delete_device_domain {
> + struct hv_input_device_domain device_domain;
> +} __packed;
> +
> +struct hv_input_attach_device_domain {
> + struct hv_input_device_domain device_domain;
> + union hv_device_id device_id;
> +} __packed;
> +
> +struct hv_input_detach_device_domain {
> + u64 partition_id;
> + union hv_device_id device_id;
> +} __packed;
> +
> +struct hv_device_domain_settings {
> + struct {
> + /*
> + * Enable translations. If not enabled, all
> transaction bypass
> + * S1 translations.
> + */
> + u64 translation_enabled: 1;
> + u64 blocked: 1;
> + /*
> + * First stage address translation paging mode:
> + * 0: 4-level paging (default)
> + * 1: 5-level paging
> + */
> + u64 first_stage_paging_mode: 1;
> + u64 reserved: 61;
> + } flags;
> +
> + /* Address of translation table */
> + u64 page_table_root;
> +} __packed;
> +
> +struct hv_input_configure_device_domain {
> + struct hv_input_device_domain device_domain;
> + struct hv_device_domain_settings settings;
> +} __packed;
> +
> +struct hv_input_get_iommu_capabilities {
> + u64 partition_id;
> + u64 reserved;
> +} __packed;
> +
> +struct hv_output_get_iommu_capabilities {
> + u32 size;
> + u16 reserved;
> + u8 max_iova_width;
> + u8 max_pasid_width;
> +
> +#define HV_IOMMU_CAP_PRESENT BIT_ULL(0)
> +#define HV_IOMMU_CAP_S2 BIT_ULL(1)
> +#define HV_IOMMU_CAP_S1 BIT_ULL(2)
> +#define HV_IOMMU_CAP_S1_5LVL BIT_ULL(3)
> +#define HV_IOMMU_CAP_PASID BIT_ULL(4)
> +#define HV_IOMMU_CAP_ATS BIT_ULL(5)
> +#define HV_IOMMU_CAP_PRI BIT_ULL(6)
> +
> + u64 iommu_cap;
> + u64 pgsize_bitmap;
> +} __packed;
> +
> +enum hv_logical_device_property_code {
> + HV_LOGICAL_DEVICE_PROPERTY_PVIOMMU = 10,
> +};
> +
> +struct hv_input_get_logical_device_property {
> + u64 partition_id;
> + u64 logical_device_id;
> + /* Takes values from enum hv_logical_device_property_code. */
> + u32 code;
> + u32 reserved;
> +} __packed;
> +
> +struct hv_output_get_logical_device_property {
> +#define HV_DEVICE_IOMMU_ENABLED BIT_ULL(0)
> + u64 device_iommu;
> + u64 reserved;
> +} __packed;
> +
> +struct hv_input_flush_device_domain {
> + struct hv_input_device_domain device_domain;
> + u32 flags;
> + u32 reserved;
> +} __packed;
> +
> #endif /* _HV_HVHDK_MINI_H */
Reviewed-by: Jacob Pan <jacob.pan@xxxxxxxxxxxxxxxxxxx>