get_update_locks_for_mdev(9)

💅 get_update_locks_for_mdev — the kernel API manual, bestie edition 🎀

okay so picture this: it's a Kernel API Manual page, and the star of the show is get_update_locks_for_mdev. She grabs all the locks you need to dynamically update a KVM guest's APCB — and she grabs them in the correct order, because order is literally everything here. periodt. 👑

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✨ SYNOPSIS ✨

void get_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. She's holding the AP configuration data you're gonna use to update a KVM guest's APCB. that's her whole job tbh 🫶

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🔥 DESCRIPTION 🔥

the way this function works is honestly so organized of her. the proper locking order is exactly this, no improvising, no vibes-based reordering:

1. matrix_dev->guests_lock — required to use the KVM pointer to update a KVM guest's APCB.
2. matrix_mdev->kvm->lock — required to update a guest's APCB.
3. matrix_dev->mdevs_lock — required to access data stored in a matrix_mdev.

like, she said "the locks come in a specific order and I'm not negotiating." iconic behavior, honestly. 💅

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🦋 NOTE 🦋

lowkey important caveat: if matrix_mdev is NULL, or it's not attached to a KVM guest, then the KVM lock will not be taken. no guest, no lock, no problem. 😌

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👑 SEE ALSO 👑

the whole friend group, in no particular order (okay, it's in this particular order):

• Kernel file ./drivers/s390/crypto/vfio_ap_ops.c
• get_update_locks_for_kvm(9)
• release_update_locks_for_kvm(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)
• 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)

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and that's the whole page, bestie 💖 this one lives over in ./drivers/s390/crypto, stamped October 2026, and it answers to the name get_update_locks_for_mdev(9). go forth and lock in the right order, ily, mwah 🧚✨