vfio_ap_mdev...y_no_sharing(9)

🦋 vfio_ap_mdev_verify_no_sharing 💅

okay bestie, welcome to the Kernel API Manual — yes we're in kernel land today, and yes this one is lowkey a bouncer at the club door of s390 crypto. The function is vfio_ap_mdev_verify_no_sharing and it's on gatekeeping duty ✨

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🌸 NAME 🌸

vfio_ap_mdev_verify_no_sharing — the function that checks your APQNs aren't being shared by matrix mdevs. no cap, that's literally its whole job 🎀

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⭐ SYNOPSIS ⭐

int vfio_ap_mdev_verify_no_sharing (struct ap_matrix_mdev *assignee ,
unsigned long *mdev_apm , unsigned long *mdev_aqm );

that's the whole signature, icon, memorize it 🫶

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💖 ARGUMENTS 💖

• assignee — the matrix mdev that mdev_apm and mdev_aqm are getting assigned to ✨ or… NULL 🙈 if this function got called by the AP bus driver in_use callback, in which case the vibe check is different: it's verifying that none of the APQNs being reserved for the host device driver are in use by a vfio_ap mediated device. two moods, one parameter 💅
• mdev_apm — the mask showing off the APIDs of the APQNs that need verifying 🔥
• mdev_aqm — and this one's the mask showing the APQIs of the APQNs that need verifying 🌈

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👑 DESCRIPTION 👑

so here's the tea 🍓 this function verifies that each APQN you get from the Cartesian product of the APIDs represented by the bits set in mdev_apm and the APQIs of the bits set in mdev_aqm is not assigned to a mediated device other than the mdev the APQN is being assigned to — that's assignee btw, keep up 💖

AP queue sharing is not allowed. periodt. hard no. 🚫

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🌸 RETURN 🌸

• 0 — the APQNs are not shared, slay, you're so valid ✅
• -EADDRINUSE — otherwise 😭 the APQNs are shared and the function is giving you that error back 💀

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✨ SEE ALSO ✨

the whole friend group, in order, no one gets left out 🫶

• Kernel file ./drivers/s390/crypto/vfio_ap_ops.c
• 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), ensure_nib_shared(9), vfio_ap_irq_enable(9)
• vfio_ap_le_guid_to_be_uuid(9), handle_pqap(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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ok and before you go — this page came from ./drivers/s390/crypto and it's dated October 2026, alongside the Kernel API Manual header up top 💜 that's the source/version/date sign-off bestie, we're done here 🧚

go forth and never share an AP queue 💅✨