[RESEND PATCH v3 0/3] Add Devres managed IRQ vectors allocation

Shawn Lin
2026-04-22T02:54:27Z

There is a long-standing design issue in the PCI/MSI subsystem where the
implicit, automatic management of IRQ vectors by the devres framework
conflicts with explicit driver cleanup, creating ambiguity and potential
resource management bugs.

Historically, pcim_enable_device() not only manages standard PCI resources
(BARs) via devres but also implicitly triggers automatic IRQ vector management
when calling pci_alloc_irq_vectors[_affinity], because pcim_enable_device()
sets is_managed flag, thus pcim_msi_release() will register a cleanup action.

This creates an ambiguous ownership model. Many drivers follow a pattern of:
1. Calling pci_alloc_irq_vectors() to allocate interrupts.
2. Also calling pci_free_irq_vectors() in their error paths or remove routines.

When such a driver also uses pcim_enable_device(), the devres framework may
attempt to free the IRQ vectors a second time upon device release, leading to
a double-free. Analysis of the tree shows this hazardous pattern exists widely,
while 35 other drivers correctly rely solely on the implicit cleanup.

This series introduces new managed APIs: pcim_alloc_irq_vectors()and
pcim_alloc_irq_vectors_affinity(). Drivers that wish to have devres-managed IRQ
vectors should use these functions. They are currently the same as non-devres
managed version. In the short term, the series converts two drivers within the
PCI subsystem to use the new APIs. The long-term goal is to convert all other
drivers which wish to use these managed functions, and finally to remove the
problematic hybrid management pattern from pcim_enable_device() and
pcim_setup_msi_release() entirely.

Changes in v3:
- Rework the commit message and function doc (Philipp)
- Remove setting is_msi_managed flag from new APIs (Philipp)

Changes in v2:
- Rebase
- Introduce patches only for PCI subsystem to convert the API

Shawn Lin (3):
PCI/MSI: Add Devres managed IRQ vectors allocation
PCI: switchtec: Replace pci_alloc_irq_vectors() with
pcim_alloc_irq_vectors()
PCI: vmd: Replace pci_alloc_irq_vectors() with
pcim_alloc_irq_vectors()

drivers/pci/controller/vmd.c | 4 ++--
drivers/pci/msi/api.c | 47 ++++++++++++++++++++++++++++++++++++++++++
drivers/pci/switch/switchtec.c | 6 +++---
include/linux/pci.h | 22 ++++++++++++++++++++
4 files changed, 74 insertions(+), 5 deletions(-)

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