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Message-Id: <20230430131518.2708471-2-alvaro.karsz@solid-run.com>
Date: Sun, 30 Apr 2023 16:15:16 +0300
From: Alvaro Karsz <alvaro.karsz@...id-run.com>
To: mst@...hat.com, jasowang@...hat.com
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
xuanzhuo@...ux.alibaba.com,
Alvaro Karsz <alvaro.karsz@...id-run.com>
Subject: [RFC PATCH net 1/3] virtio: re-negotiate features if probe fails and features are blocked
This patch exports a new virtio core function: virtio_block_feature.
The function should be called during a virtio driver probe.
If a virtio driver blocks features during probe and fails probe, virtio
core will reset the device, try to re-negotiate the new features and
probe again.
Signed-off-by: Alvaro Karsz <alvaro.karsz@...id-run.com>
---
drivers/virtio/virtio.c | 73 ++++++++++++++++++++++++++++++-----------
include/linux/virtio.h | 3 ++
2 files changed, 56 insertions(+), 20 deletions(-)
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 3893dc29eb2..eaad5b6a7a9 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -167,6 +167,13 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status)
}
EXPORT_SYMBOL_GPL(virtio_add_status);
+void virtio_block_feature(struct virtio_device *dev, unsigned int f)
+{
+ BUG_ON(f >= 64);
+ dev->blocked_features |= (1ULL << f);
+}
+EXPORT_SYMBOL_GPL(virtio_block_feature);
+
/* Do some validation, then set FEATURES_OK */
static int virtio_features_ok(struct virtio_device *dev)
{
@@ -234,17 +241,13 @@ void virtio_reset_device(struct virtio_device *dev)
}
EXPORT_SYMBOL_GPL(virtio_reset_device);
-static int virtio_dev_probe(struct device *_d)
+static int virtio_negotiate_features(struct virtio_device *dev)
{
- int err, i;
- struct virtio_device *dev = dev_to_virtio(_d);
struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
u64 device_features;
u64 driver_features;
u64 driver_features_legacy;
-
- /* We have a driver! */
- virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
+ int i, ret;
/* Figure out what features the device supports. */
device_features = dev->config->get_features(dev);
@@ -279,30 +282,61 @@ static int virtio_dev_probe(struct device *_d)
if (device_features & (1ULL << i))
__virtio_set_bit(dev, i);
- err = dev->config->finalize_features(dev);
- if (err)
- goto err;
+ /* Remove blocked features */
+ dev->features &= ~dev->blocked_features;
+
+ ret = dev->config->finalize_features(dev);
+ if (ret)
+ goto exit;
if (drv->validate) {
u64 features = dev->features;
- err = drv->validate(dev);
- if (err)
- goto err;
+ ret = drv->validate(dev);
+ if (ret)
+ goto exit;
/* Did validation change any features? Then write them again. */
if (features != dev->features) {
- err = dev->config->finalize_features(dev);
- if (err)
- goto err;
+ ret = dev->config->finalize_features(dev);
+ if (ret)
+ goto exit;
}
}
- err = virtio_features_ok(dev);
- if (err)
- goto err;
+ ret = virtio_features_ok(dev);
+exit:
+ return ret;
+}
+
+static int virtio_dev_probe(struct device *_d)
+{
+ int err;
+ struct virtio_device *dev = dev_to_virtio(_d);
+ struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+ u64 blocked_features;
+ bool renegotiate = true;
+
+ /* We have a driver! */
+ virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
+
+ /* Store blocked features and attempt to negotiate features & probe.
+ * If the probe fails, we check if the driver has blocked any new features.
+ * If it has, we reset the device and try again with the new features.
+ */
+ while (renegotiate) {
+ blocked_features = dev->blocked_features;
+ err = virtio_negotiate_features(dev);
+ if (err)
+ break;
+
+ err = drv->probe(dev);
+ if (err && blocked_features != dev->blocked_features)
+ virtio_reset_device(dev);
+ else
+ renegotiate = false;
+ }
- err = drv->probe(dev);
if (err)
goto err;
@@ -319,7 +353,6 @@ static int virtio_dev_probe(struct device *_d)
err:
virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
return err;
-
}
static void virtio_dev_remove(struct device *_d)
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index b93238db94e..2de9b2d3ca4 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -109,6 +109,7 @@ int virtqueue_resize(struct virtqueue *vq, u32 num,
* @vringh_config: configuration ops for host vrings.
* @vqs: the list of virtqueues for this device.
* @features: the features supported by both driver and device.
+ * @blocked_features: the features blocked by the driver that can't be negotiated.
* @priv: private pointer for the driver's use.
*/
struct virtio_device {
@@ -124,6 +125,7 @@ struct virtio_device {
const struct vringh_config_ops *vringh_config;
struct list_head vqs;
u64 features;
+ u64 blocked_features;
void *priv;
};
@@ -133,6 +135,7 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status);
int register_virtio_device(struct virtio_device *dev);
void unregister_virtio_device(struct virtio_device *dev);
bool is_virtio_device(struct device *dev);
+void virtio_block_feature(struct virtio_device *dev, unsigned int f);
void virtio_break_device(struct virtio_device *dev);
void __virtio_unbreak_device(struct virtio_device *dev);
--
2.34.1
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