Re: [PATCH v2 07/10] selftests/vfio: Add vfio_pci_irq_reenable() helper

[David Matlack <dmatlack@google.com>]

On 2026-05-26 11:54 PM, Josh Hilke wrote:
> From: Alex Williamson <alex.williamson@nvidia.com>
> 
> Selftest drivers that recover from a fault by issuing VFIO_DEVICE_RESET
> need to re-arm device interrupts afterwards.  VFIO_DEVICE_RESET tears
> down the kernel-side IRQ trigger so a subsequent VFIO_DEVICE_SET_IRQS
> is required, but the user-side eventfds (and any fd cached in a test
> fixture) are still valid and must be preserved.
> 
> vfio_pci_irq_enable() refuses to be called for vectors that already
> have an eventfd (VFIO_ASSERT_LT), and vfio_pci_irq_disable() closes
> all eventfds before resetting the trigger, so neither is suitable.
> 
> Add vfio_pci_irq_reenable(device, index, vector, count) which asserts
> that the requested range has existing eventfds and re-issues
> VFIO_DEVICE_SET_IRQS using them.  Signature mirrors vfio_pci_irq_enable().
> 
> Assisted-by: Claude:claude-opus-4-7
> Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
> ---
>  .../lib/include/libvfio/vfio_pci_device.h     |  2 ++
>  .../selftests/vfio/lib/vfio_pci_device.c      | 22 +++++++++++++++++++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
> index 2858885a89bb..a362e2b2bfda 100644
> --- a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
> +++ b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
> @@ -68,6 +68,8 @@ void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
>  void vfio_pci_irq_enable(struct vfio_pci_device *device, u32 index,
>  			 u32 vector, int count);
>  void vfio_pci_irq_disable(struct vfio_pci_device *device, u32 index);
> +void vfio_pci_irq_reenable(struct vfio_pci_device *device, u32 index,
> +			   u32 vector, int count);

Let's add vfio_pci_msi{,x}_reenable() static inline wrappers below
alongside the existing enable/disable wrappers. And use the msix helper
in the next driver patch for consistency.

>  void vfio_pci_irq_trigger(struct vfio_pci_device *device, u32 index, u32 vector);
>  
>  static inline void fcntl_set_nonblock(int fd)
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> index fc75e04ef010..7b8394d0ac50 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> @@ -106,6 +106,28 @@ void vfio_pci_irq_disable(struct vfio_pci_device *device, u32 index)
>  	vfio_pci_irq_set(device, index, 0, 0, NULL);
>  }
>  
> +/*
> + * Re-issue VFIO_DEVICE_SET_IRQS for an already-enabled vector range using
> + * the existing eventfds.  Intended for drivers that need to re-arm device
> + * interrupts after a VFIO_DEVICE_RESET, which tears down the kernel-side
> + * IRQ trigger but leaves user-side eventfds intact.  Recreating the
> + * eventfds would invalidate any test-fixture cache of the fd, so this
> + * helper deliberately preserves them.
> + */
> +void vfio_pci_irq_reenable(struct vfio_pci_device *device, u32 index,
> +			   u32 vector, int count)
> +{
> +	int i;
> +
> +	check_supported_irq_index(index);
> +
> +	for (i = vector; i < vector + count; i++)
> +		VFIO_ASSERT_GE(device->msi_eventfds[i], 0,
> +			       "vector %d eventfd not allocated\n", i);
> +
> +	vfio_pci_irq_set(device, index, vector, count, device->msi_eventfds + vector);
> +}
> +
>  static void vfio_pci_irq_get(struct vfio_pci_device *device, u32 index,
>  			     struct vfio_irq_info *irq_info)
>  {
> -- 
> 2.54.0.794.g4f17f83d09-goog
>