[PATCH v5 0/3] genirq/vfio: Introduce irq_update_devid() and optimize VFIO irq ops

[Ben Luo]

Currently, VFIO takes a free-then-request-irq way to do interrupt
affinity setting and masking/unmasking for a VM (with device passthru
via VFIO). Sometimes it only changes the cookie data of irqaction or even
changes nothing. The free-then-request-irq not only adds more latency,
but also increases the risk of losing interrupt, which may lead to a
VM hung forever in waiting for IO completion

This patchset solved the issue by:
Patch 2 introduces irq_update_devid() to only update dev_id of irqaction
Patch 3 make use of this function and optimize irq operations in VFIO

changes from v4:
 - Patch 3: follow the previous behavior to disable interrupt on error path
 - Patch 3: do irqbypass registration before update or free the interrupt
 - Patch 3: add more comments

changes from v3:
 - Patch 2: rename the new function to irq_update_devid()
 - Patch 2: use disbale_irq() to avoid a twist for threaded interrupt
 - ALL: amend commit messages and code comments

changes from v2:
 - reformat to avoid quoted string split across lines and etc.

changes from v1:
 - add Patch 1 to enhance error recovery etc. in free irq per tglx's comments
 - enhance error recovery code and debugging info in irq_update_devid
 - use __must_check in external referencing of this function
 - use EXPORT_SYMBOL_GPL for irq_update_devid
 - reformat code of patch 3 for better readability

Ben Luo (3):
  genirq: enhance error recovery code in free irq
  genirq: introduce irq_update_devid()
  vfio/pci: make use of irq_update_devid and optimize irq ops

 drivers/vfio/pci/vfio_pci_intrs.c | 124 ++++++++++++++++++++++++++------------
 include/linux/interrupt.h         |   3 +
 kernel/irq/manage.c               | 105 ++++++++++++++++++++++++++++----
 3 files changed, 183 insertions(+), 49 deletions(-)

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1.8.3.1