STRUCT IOMMUFD_VEVENT_HEADER(9)

💖 NAME 💖

okay so welcome to the Kernel API Manual, bestie — this page is struct iommufd_vevent_header(9) (the running header up top truncates it all cute-like as struct iommu...event_header(9), don't let that jump-scare you). It's the Virtual Event Header for a vEVENTQ Status. yes, that is literally the whole job. she's a header. she reports things. iconic.

---

✨ SYNOPSIS ✨

struct iommufd_vevent_header {
    __u32 flags;
    __u32 sequence;
 };

two __u32s. that's the whole struct. tiny queen, massive responsibilities 💅

---

🎀 Members 🎀

• flags — a combination of enum iommu_veventq_flag. like a little bitmask mood ring 🌀
• sequence — the sequence index of a vEVENT in the vEVENTQ, with a range of [0, INT_MAX], where the following index of INT_MAX is 0. so yeah, it wraps. INT_MAX ain't the end, it's just the last stop before we loop back to 0 🔁

---

🌸 Description 🌸

okay so here's the vibe: each iommufd_vevent_header reports a sequence index of the following vEVENT. picture it like this 🎀

┌───────────────────────────────────────────────────────────────────────────┐
│ header0 {sequence=0}   data0   header1 {sequence=1}   data1   ...   dataN │
└───────────────────────────────────────────────────────────────────────────┘

and this sequence index is expected to be monotonic to the sequence index of the previous vEVENT. meaning: it goes up, it doesn't do chaotic little backwards flips. fr fr.

if two adjacent sequence indexes has a delta larger than 1, it means that delta - 1 number of vEVENTs has lost — e.g. two lost vEVENTs: 😭 so if you see a jump, count the gap and that's how many events ghosted you.

and if a vEVENT lost at the tail of the vEVENTQ and there is no following vEVENT providing the next sequence index, an IOMMU_VEVENTQ_FLAG_LOST_EVENTS header would be added to the tail, and no data would follow this header. so the last one's a little flag-only announcement, no payload attached. she said "just so you know" and left 🫶

---

🦋 SEE ALSO 🦋

the whole group chat, in order, no one left out 💜

• Kernel file ./include/uapi/linux/iommufd.h
• General ioctl format(9)
• struct iommu_destroy(9)
• struct iommu_ioas_alloc(9)
• struct iommu_iova_range(9)
• struct iommu_ioas_iova_ranges(9)
• struct iommu_ioas_allow_iovas(9)
• enum iommufd_ioas_map_flags(9)
• struct iommu_ioas_map(9)
• struct iommu_ioas_noiommu_get_pa(9)
• struct iommu_ioas_map_file(9)
• struct iommu_ioas_copy(9)
• struct iommu_ioas_unmap(9)
• enum iommufd_option(9)
• enum iommufd_option_ops(9)
• struct iommu_option(9)
• enum iommufd_vfio_ioas_op(9)
• struct iommu_vfio_ioas(9)
• enum iommufd_hwpt_alloc_flags(9)
• enum iommu_hwpt_vtd_s1_flags(9)
• struct iommu_hwpt_vtd_s1(9)
• struct iommu_hwpt_arm_smmuv3(9)
• struct iommu_hwpt_amd_guest(9)
• enum iommu_hwpt_data_type(9)
• struct iommu_hwpt_alloc(9)
• enum iommu_hw_info_vtd_flags(9)
• struct iommu_hw_info_vtd(9)
• enum iommu_hw_info_arm_smmuv3_flags(9)
• struct iommu_hw_info_arm_smmuv3(9)
• struct iommu_hw_info_tegra241_cmdqv(9)
• struct iommu_hw_info_amd(9)
• enum iommu_hw_info_type(9)
• enum iommufd_hw_capabilities(9)
• enum iommufd_hw_info_flags(9)
• struct iommu_hw_info(9)
• struct iommu_hwpt_set_dirty_tracking(9)
• enum iommufd_hwpt_get_dirty_bitmap_flags(9)
• struct iommu_hwpt_get_dirty_bitmap(9)
• enum iommu_hwpt_invalidate_data_type(9)
• enum iommu_hwpt_vtd_s1_invalidate_flags(9)
• struct iommu_hwpt_vtd_s1_invalidate(9)
• struct iommu_viommu_arm_smmuv3_invalidate(9)
• struct iommu_hwpt_invalidate(9)
• enum iommu_hwpt_pgfault_flags(9)
• enum iommu_hwpt_pgfault_perm(9)
• struct iommu_hwpt_pgfault(9)
• enum iommufd_page_response_code(9)
• struct iommu_hwpt_page_response(9)
• struct iommu_fault_alloc(9)
• enum iommu_viommu_type(9)
• struct iommu_viommu_tegra241_cmdqv(9)
• struct iommu_viommu_alloc(9)
• struct iommu_vdevice_alloc(9)
• struct iommu_ioas_change_process(9)
• enum iommu_veventq_flag(9)
• enum iommu_veventq_type(9)
• struct iommu_vevent_arm_smmuv3(9)
• struct iommu_vevent_tegra241_cmdqv(9)
• struct iommu_veventq_alloc(9)
• enum iommu_hw_queue_type(9)
• struct iommu_hw_queue_alloc(9)

---

that's the whole page, no cap. she lives in ./include/uapi/linux, she's stamped October 2026, and the footer insists on spelling herself struct iommu...event_header(9) one more time for the cheap seats. mwah 💋 go read the rest of the kernel, bestie 🌈⭐