From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Jasper Wise <jaspwise@amazon.co.uk>,
	Mark Brown <broonie@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18 214/217] spi: virtio: mark device ready before registering the controller
Date: Thu, 20 Aug 2026 16:56:22 +0200
Message-ID: <20260820145244.125653610@linuxfoundation.org>
In-Reply-To: <20260820145237.531699751@linuxfoundation.org>
References: <20260820145237.531699751@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jasper Wise <jaspwise@amazon.co.uk>

[ Upstream commit 11058bd3d47d57eb3473935feae53868d6d168b7 ]

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>
Link: https://patch.msgid.link/20260813084618.613172-1-jaspwise@amazon.co.uk
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 2acb929b2c690..fb30c9207a4b0 100644
--- a/drivers/spi/spi-virtio.c
+++ b/drivers/spi/spi-virtio.c
@@ -361,6 +361,8 @@ 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)
-- 
2.53.0