Re: [PATCH v7 5/6] vfio: selftests: Retry on EAGAIN during device reset

[Alex Williamson <alex@shazbot.org>]

On Tue, 28 Jul 2026 23:24:30 +0000
Josh Hilke <jrhilke@google.com> wrote:

> Add retry logic to vfio_pci_device_reset() to handle the case where PCI
> resets fail due to lock contention, in which case
> pci_try_reset_function() returns -EAGAIN.
> 
> Suggested-by: David Matlack <dmatlack@google.com>
> Signed-off-by: Josh Hilke <jrhilke@google.com>
> ---
>  .../vfio/lib/include/libvfio/vfio_pci_device.h          |  1 +
>  tools/testing/selftests/vfio/lib/vfio_pci_device.c      | 17 ++++++++++++++++-
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> 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 2e67afc0d580..27bdf561925f 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
> @@ -41,6 +41,7 @@ struct vfio_pci_device {
>  struct vfio_pci_device *vfio_pci_device_init(const char *bdf, struct iommu *iommu);
>  void vfio_pci_device_cleanup(struct vfio_pci_device *device);
>  
> +int __vfio_pci_device_reset(struct vfio_pci_device *device);
>  void vfio_pci_device_reset(struct vfio_pci_device *device);
>  
>  void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> index 7b8394d0ac50..1b29cef96b04 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  #include <dirent.h>
> +#include <errno.h>
>  #include <fcntl.h>
>  #include <libgen.h>
>  #include <stdint.h>
> @@ -221,9 +222,23 @@ void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
>  		       write ? "write to" : "read from", config);
>  }
>  
> +int __vfio_pci_device_reset(struct vfio_pci_device *device)
> +{
> +	if (ioctl(device->fd, VFIO_DEVICE_RESET, NULL))
> +		return -errno;
> +
> +	return 0;
> +}
> +
>  void vfio_pci_device_reset(struct vfio_pci_device *device)
>  {
> -	ioctl_assert(device->fd, VFIO_DEVICE_RESET, NULL);
> +	int r;
> +
> +	do {
> +		r = __vfio_pci_device_reset(device);
> +	} while (r == -EAGAIN);
> +
> +	VFIO_ASSERT_EQ(r, 0, "ioctl(device->fd, VFIO_DEVICE_RESET) failed\n");
>  }

This has roughly the same unbounded loop issue that Sashiko flagged
waiting for the register level reset to complete, shouldn't we also
introduce a retry cap here?  A delay would also help bound that retry
cap versus the instant retry here.

Also, please rebase to linux-next to keep the driver inclusion
consistent with the already merged nv_falcon driver (trivial) and
unblock Sashiko from applying the series for review (more important).
David's R-bs from v6 can also carry forward on the unmodified patches.
Thanks,

Alex