ensure_nib_shared(9)

💅 ensure_nib_shared(9) — the kernel API manual, bestie edition

okay so this whole page lives in the Kernel API Manual and it's literally all about ensure_nib_shared(9). buckle up 🎀

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✨ NAME ✨

ensure_nib_shared — bestie, it makes sure the address of the NIB is secure and shared. that's the whole vibe check 🔥

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🌸 SYNOPSIS 🌸

int ensure_nib_shared (unsigned long addr );

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🦋 ARGUMENTS 🦋

• addr — the physical (absolute) address of the NIB. like, the actual literal address, not a vibe. 📍

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💖 DESCRIPTION 💖

so this function checks whether the NIB page — which has been pinned with vfio_pin_pages — is a shared page belonging to a secure guest. 👑

it will call uv_pin_shared on it. and if the page was already pinned shared (i.e. if the NIB belongs to a secure guest and is shared), then 0 (success) is returned. slay. ✨

but if the NIB was not shared, then vfio_pin_pages had exported it and now it does not belong to the secure guest anymore 😭 in that case, an error is returned. no cap, that's the sad path.

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🫶 CONTEXT 🫶

the NIB (at physical address addr) has to be pinned with vfio_pin_pages before calling this function. like, do the pinning first, then come talk to me. 💅

fr fr bestie, pinned first or this whole thing is giving undefined chaos 🙈

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⭐ RETURN ⭐

0 in case of success, otherwise an error < 0. that's it, that's the whole report card. 💀

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🌈 SEE ALSO 🌈

kernel file ./drivers/s390/crypto/vfio_ap_ops.c — go read the source, iykyk 📖

• get_update_locks_for_kvm(9)
• release_update_locks_for_kvm(9)
• get_update_locks_for_mdev(9)
• release_update_locks_for_mdev(9)
• get_update_locks_by_apqn(9)
• get_update_locks_for_queue(9)
• vfio_ap_mdev_get_queue(9)
• vfio_ap_wait_for_irqclear(9)
• vfio_ap_free_aqic_resources(9)
• vfio_ap_irq_disable(9)
• vfio_ap_validate_nib(9)
• vfio_ap_irq_enable(9)
• vfio_ap_le_guid_to_be_uuid(9)
• handle_pqap(9)
• vfio_ap_mdev_verify_no_sharing(9)
• vfio_ap_mdev_validate_masks(9)
• assign_adapter_store(9)
• vfio_ap_mdev_unlink_adapter(9)
• unassign_adapter_store(9)
• assign_domain_store(9)
• unassign_domain_store(9)
• assign_control_domain_store(9)
• unassign_control_domain_store(9)
• vfio_ap_mdev_set_kvm(9)
• vfio_ap_mdev_unset_kvm(9)
• vfio_ap_mdev_resource_in_use(9)
• vfio_ap_mdev_hot_unplug_cfg(9)
• vfio_ap_mdev_cfg_remove(9)
• vfio_ap_mdev_on_cfg_remove(9)
• vfio_ap_filter_apid_by_qtype(9)
• vfio_ap_mdev_cfg_add(9)
• vfio_ap_mdev_on_cfg_add(9)
• vfio_ap_on_cfg_changed(9)

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okay and for the cute sign-off 🎀: this whole thing comes from the kernel file ./drivers/s390/crypto, dated October 2026, and it's filed under ensure_nib_shared(9). mwah, go pin some pages bestie 💜🧚