virtio_spi_probe() registers the SPI controller with
devm_spi_register_controller(). spi_register_controller() binds a child
inline unless its driver has asked for asynchronous probing, so a
peripheral that performs a transfer during its own probe reaches
virtio_spi_transfer_one(), which kicks the virtqueue before probe has
returned.

The driver never calls virtio_device_ready(), so DRIVER_OK is set on its
behalf by virtio_dev_probe(), only once probe has returned. The virtio
spec is explicit about that ordering in 3.1 Device Initialization:
  |  The driver MUST NOT send any buffer available notifications to the
  |  device before setting DRIVER_OK.

A device that waits for DRIVER_OK before servicing the queue therefore
leaves the transfer unanswered, and virtio_spi_transfer_one() waits for its
completion with no timeout, so probe never returns.

Mark the device ready before registering the controller, as done for the
same reason in commit f5866db64f34 ("virtio_console: enable VQs early") and
commit 1d774589f924 ("i2c: virtio: mark device ready before registering the
adapter").

Fixes: f98cabe3f6cf ("SPI: Add virtio SPI driver")
Signed-off-by: Jasper Wise <jaspwise@amazon.co.uk>
---
 drivers/spi/spi-virtio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi-virtio.c b/drivers/spi/spi-virtio.c
index fa4c68049eca..2256dfec5407 100644
--- a/drivers/spi/spi-virtio.c
+++ b/drivers/spi/spi-virtio.c
@@ -358,6 +358,8 @@ static int virtio_spi_probe(struct virtio_device *vdev)
 	if (ret)
 		return dev_err_probe(&vdev->dev, ret, "Cannot register virtqueue cleanup\n");
 
+	virtio_device_ready(vdev);
+
 	/* Use devm version to register controller */
 	ret = devm_spi_register_controller(&vdev->dev, ctrl);
 	if (ret)

base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
-- 
2.50.1

On Thu, 13 Aug 2026 08:46:18 +0000, Jasper Wise wrote:
> spi: virtio: mark device ready before registering the controller

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-7.2

Thanks!

[1/1] spi: virtio: mark device ready before registering the controller
      https://git.kernel.org/broonie/spi/c/11058bd3d47d

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark