get_update_locks_for_kvm(9)

💅 get_update_locks_for_kvm — from the Kernel API Manual, bestie

okay so this one's a locking page from the kernel API manual, and honestly? it's giving "VIP queue at the club" energy. because that's literally what it is — grabbing a whole stack of locks in exactly the right order or everything falls apart. no pressure 🫶

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✨ NAME ✨

get_update_locks_for_kvm — grabs every lock you need to dynamically update a KVM guest's APCB, and grabs them in the correct order, because order is everything here 🔥

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🌸 SYNOPSIS 🌸

void get_update_locks_for_kvm (struct kvm *kvm );

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🎀 ARGUMENTS 🎀

• kvm — a pointer to a struct kvm object that holds the KVM guest's APCB. that's the whole vibe. 💖

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🦋 DESCRIPTION 🦋

so the proper locking order is this, and you cannot freestyle it — it's a numbered list for a reason, bestie:

1. matrix_dev->guests_lock: needed so you can use the KVM pointer to update a KVM guest's APCB.
2. kvm->lock: needed to update a guest's APCB.
3. kvm->arch.crypto.pqap_hook_rwsem: needed to update pqap_hook, and it serializes against PQAP intercepts.
4. matrix_dev->mdevs_lock: needed to access data stored in a matrix_mdev.

like… lock one, lock two, lock three, lock four. in that order. periodt. 💅

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👑 NOTE 👑

if kvm is NULL, the KVM lock and pqap_hook_rwsem will not be taken. so like, they just don't show up to the party. noted. 🫡

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🌈 SEE ALSO 🌈

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

and the whole friend group 💜:

• 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)
• 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 lil icon lives in ./drivers/s390/crypto, dated October 2026, and it ate, no cap. mwah 🎀✨👑