msi_device_has_isolated_msi(9)

okay so bestie, this is the Kernel API Manual page for msi_device_has_isolated_msi(9) — yes, we’re in kernel-internals territory and it’s lowkey iconic. 💅✨

🌸 NAME 🌸

msi_device_has_isolated_msi — true if the device has isolated MSI. That’s the whole name, and it’s giving “security vibe check” energy. 🫶

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✨ SYNOPSIS ✨

Here’s the signature, exactly as it is — no cap:

bool msi_device_has_isolated_msi (struct device *dev );

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🎀 ARGUMENTS 🎀

• dev — the device to check. That’s it; one argument, main character energy. 💖

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🦋 DESCRIPTION 🦋

okay so, isolated MSI means that HW modeled by an irq_domain on the path from the initiating device to the CPU will validate that the MSI message specifies an interrupt number that the device is authorized to trigger. It’s literally a vibe check for interrupt permissions. 🔥

This must block devices from triggering interrupts they are not authorized to trigger. Currently, authorization means the MSI vector is one assigned to the device. Periodt. 💅

This is interesting for securing VFIO use cases where a rouge MSI (eg created by abusing a normal PCI MemWr DMA) must not allow the VFIO userspace to impact outside its security domain, eg userspace triggering interrupts on kernel drivers, a VM triggering interrupts on the hypervisor, or a VM triggering interrupts on another VM. That’s the whole “stay in your lane” security moment, bestie. 😭👑

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🌈 SEE ALSO 🌈

Kernel file ./kernel/irq/msi.c — and the whole squad is:

• struct msi_device_data(9)
• struct msi_ctrl(9)
• msi_alloc_desc(9)
• msi_domain_insert_msi_desc(9)
• msi_domain_free_msi_descs_range(9)
• msi_domain_add_simple_msi_descs(9)
• msi_setup_device_data(9)
• __msi_lock_descs(9)
• __msi_unlock_descs(9)
• msi_domain_first_desc(9)
• msi_next_desc(9)
• msi_domain_get_virq(9)
• msi_device_populate_sysfs(9)
• msi_device_destroy_sysfs(9)
• msi_domain_set_affinity(9)
• msi_create_irq_domain(9)
• msi_create_parent_irq_domain(9)
• msi_parent_init_dev_msi_info(9)
• msi_create_device_irq_domain(9)
• msi_remove_device_irq_domain(9)
• msi_match_device_irq_domain(9)
• msi_domain_alloc_irqs_range_locked(9)
• msi_domain_alloc_irqs_range(9)
• msi_domain_alloc_irqs_all_locked(9)
• msi_domain_alloc_irq_at(9)
• msi_device_domain_alloc_wired(9)
• msi_domain_free_irqs_range_locked(9)
• msi_domain_free_irqs_range(9)
• msi_domain_free_irqs_all_locked(9)
• msi_domain_free_irqs_all(9)
• msi_device_domain_free_wired(9)
• msi_get_domain_info(9)

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Signed off with source/version ./kernel/irq and the date October 2026, for the page msi_device_has_isolated_msi(9) — slay, bye bestie! 💖✨🎀