release_upd...cks_for_mdev(9)

💅 release_update_locks_for_mdev(9) — the Kernel API Manual, bestie

okay so picture this: you're deep in the kernel, you just finished updating a KVM guest's APCB, and now you have to let go of the locks in exactly the right order or everything's gonna be a mess. That's this function. It's from the Kernel API Manual and honestly? It's giving "quietly iconic cleanup era." 🎀

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✨ NAME ✨

release_update_locks_for_mdev — releases the locks used to dynamically update a KVM guest's APCB, in the proper order. no cap, the order is the whole point. 🦋

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🌸 SYNOPSIS 🌸

void release_update_locks_for_mdev (struct ap_matrix_mdev *matrix_mdev
);

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💖 ARGUMENTS 💖

• matrix_mdev — a pointer to a struct ap_matrix_mdev object containing the AP configuration data to use to update a KVM guest's APCB. like, that's the data you're working with. 🫶

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🔥 DESCRIPTION 🔥

The proper unlocking order is literally this, do not freestyle it:

1. matrix_dev->mdevs_lock
2. matrix_mdev->kvm->lock
3. matrix_dev->guests_lock

that's the sequence. that's the vibe check. release them out of order and, well, the manpage doesn't even want to talk about it. 😭

the ordering is the whole personality of this function — item 1, then 2, then 3. periodt. 👑

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🙈 NOTE 🙈

If matrix_mdev is NULL or is not attached to a KVM guest, the KVM lock will not be released. so like… don't count on it. it's not being shady, it's just how it is. 💀

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🧚 SEE ALSO 🧚

Kernel file ./drivers/s390/crypto/vfio_ap_ops.c — that's where the magic lives.

• get_update_locks_for_kvm(9)
• release_update_locks_for_kvm(9)
• get_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)
• ensure_nib_shared(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)

like yes that's a lot of friends but they're all important, i don't make the rules 💜

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mwah, that's the page! 🌈 this lil masterpiece lives at ./drivers/s390/crypto and it dropped in October 2026 — go read it, slay, and always unlock in order. 💅✨