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Subject[PATCH V3 1/2] virtio: introduce methods of sanitizing device features
Date
Buggy host may advertised buggy host features (a usual case is that host
advertise a feature whose dependencies were missed). In this case, driver
should detect and disable the buggy features by itself.

This patch introduces driver specific sanitize_features() method which is
called just before features finalizing to detect and disable buggy features
advertised by host.

Virtio-net will be the first user.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes from V2:
- fix typo
- rename fix_features to sanitize_features
---
drivers/virtio/virtio.c | 4 ++++
include/linux/virtio.h | 1 +
include/linux/virtio_config.h | 12 ++++++++++++
3 files changed, 17 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index df598dd..6a86b4f 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -181,6 +181,10 @@ static int virtio_dev_probe(struct device *_d)
if (device_features & (1 << i))
set_bit(i, dev->features);

+ /* Sanitize buggy features advertised by host */
+ if (drv->sanitize_features)
+ drv->sanitize_features(dev);
+
dev->config->finalize_features(dev);

err = drv->probe(dev);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 65261a7..5aed283 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -142,6 +142,7 @@ struct virtio_driver {
void (*scan)(struct virtio_device *dev);
void (*remove)(struct virtio_device *dev);
void (*config_changed)(struct virtio_device *dev);
+ void (*sanitize_features)(struct virtio_device *dev);
#ifdef CONFIG_PM
int (*freeze)(struct virtio_device *dev);
int (*restore)(struct virtio_device *dev);
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 7f4ef66..7bd89ea 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -96,6 +96,18 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
return test_bit(fbit, vdev->features);
}

+static inline void virtio_disable_feature(struct virtio_device *vdev,
+ unsigned int fbit)
+{
+ BUG_ON(fbit >= VIRTIO_TRANSPORT_F_START);
+ BUG_ON(vdev->config->get_status(vdev) &
+ ~(VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER));
+
+ virtio_check_driver_offered_feature(vdev, fbit);
+
+ clear_bit(fbit, vdev->features);
+}
+
static inline
struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
vq_callback_t *c, const char *n)
--
1.9.1


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