From c45a6816c19dee67b8f725e6646d428901a6dc24 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 2 May 2008 21:50:50 -0500 Subject: virtio: explicit advertisement of driver features A recent proposed feature addition to the virtio block driver revealed some flaws in the API: in particular, we assume that feature negotiation is complete once a driver's probe function returns. There is nothing in the API to require this, however, and even I didn't notice when it was violated. So instead, we require the driver to specify what features it supports in a table, we can then move the feature negotiation into the virtio core. The intersection of device and driver features are presented in a new 'features' bitmap in the struct virtio_device. Note that this highlights the difference between Linux unsigned-long bitmaps where each unsigned long is in native endian, and a straight-forward little-endian array of bytes. Drivers can still remove feature bits in their probe routine if they really have to. API changes: - dev->config->feature() no longer gets and acks a feature. - drivers should advertise their features in the 'feature_table' field - use virtio_has_feature() for extra sanity when checking feature bits Signed-off-by: Rusty Russell --- drivers/virtio/virtio.c | 38 ++++++++++++++++++++++++++++++++++++-- drivers/virtio/virtio_balloon.c | 6 +++++- drivers/virtio/virtio_pci.c | 30 +++++++++++++++--------------- 3 files changed, 56 insertions(+), 18 deletions(-) (limited to 'drivers/virtio') diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index b535483..1386678 100644 --- a/drivers/virtio/virtio.c +++ b/drivers/virtio/virtio.c @@ -80,19 +80,51 @@ static void add_status(struct virtio_device *dev, unsigned status) dev->config->set_status(dev, dev->config->get_status(dev) | status); } +void virtio_check_driver_offered_feature(const struct virtio_device *vdev, + unsigned int fbit) +{ + unsigned int i; + struct virtio_driver *drv = container_of(vdev->dev.driver, + struct virtio_driver, driver); + + for (i = 0; i < drv->feature_table_size; i++) + if (drv->feature_table[i] == fbit) + return; + BUG(); +} +EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature); + static int virtio_dev_probe(struct device *_d) { - int err; + int err, i; struct virtio_device *dev = container_of(_d,struct virtio_device,dev); struct virtio_driver *drv = container_of(dev->dev.driver, struct virtio_driver, driver); + u32 device_features; + /* We have a driver! */ add_status(dev, VIRTIO_CONFIG_S_DRIVER); + + /* Figure out what features the device supports. */ + device_features = dev->config->get_features(dev); + + /* Features supported by both device and driver into dev->features. */ + memset(dev->features, 0, sizeof(dev->features)); + for (i = 0; i < drv->feature_table_size; i++) { + unsigned int f = drv->feature_table[i]; + BUG_ON(f >= 32); + if (device_features & (1 << f)) + set_bit(f, dev->features); + } + err = drv->probe(dev); if (err) add_status(dev, VIRTIO_CONFIG_S_FAILED); - else + else { add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK); + /* They should never have set feature bits beyond 32 */ + dev->config->set_features(dev, dev->features[0]); + } return err; } @@ -114,6 +146,8 @@ static int virtio_dev_remove(struct device *_d) int register_virtio_driver(struct virtio_driver *driver) { + /* Catch this early. */ + BUG_ON(driver->feature_table_size && !driver->feature_table); driver->driver.bus = &virtio_bus; driver->driver.probe = virtio_dev_probe; driver->driver.remove = virtio_dev_remove; diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index fef88d8..bfef604 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -227,7 +227,7 @@ static int virtballoon_probe(struct virtio_device *vdev) } vb->tell_host_first - = vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); + = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); return 0; @@ -259,7 +259,11 @@ static void virtballoon_remove(struct virtio_device *vdev) kfree(vb); } +static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST }; + static struct virtio_driver virtio_balloon = { + .feature_table = features, + .feature_table_size = ARRAY_SIZE(features), .driver.name = KBUILD_MODNAME, .driver.owner = THIS_MODULE, .id_table = id_table, diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c index de102a6..27e9fc9 100644 --- a/drivers/virtio/virtio_pci.c +++ b/drivers/virtio/virtio_pci.c @@ -87,23 +87,22 @@ static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev) return container_of(vdev, struct virtio_pci_device, vdev); } -/* virtio config->feature() implementation */ -static bool vp_feature(struct virtio_device *vdev, unsigned bit) +/* virtio config->get_features() implementation */ +static u32 vp_get_features(struct virtio_device *vdev) +{ + struct virtio_pci_device *vp_dev = to_vp_device(vdev); + + /* When someone needs more than 32 feature bits, we'll need to + * steal a bit to indicate that the rest are somewhere else. */ + return ioread32(vp_dev->ioaddr + VIRTIO_PCI_HOST_FEATURES); +} + +/* virtio config->set_features() implementation */ +static void vp_set_features(struct virtio_device *vdev, u32 features) { struct virtio_pci_device *vp_dev = to_vp_device(vdev); - u32 mask; - - /* Since this function is supposed to have the side effect of - * enabling a queried feature, we simulate that by doing a read - * from the host feature bitmask and then writing to the guest - * feature bitmask */ - mask = ioread32(vp_dev->ioaddr + VIRTIO_PCI_HOST_FEATURES); - if (mask & (1 << bit)) { - mask |= (1 << bit); - iowrite32(mask, vp_dev->ioaddr + VIRTIO_PCI_GUEST_FEATURES); - } - return !!(mask & (1 << bit)); + iowrite32(features, vp_dev->ioaddr + VIRTIO_PCI_GUEST_FEATURES); } /* virtio config->get() implementation */ @@ -293,7 +292,6 @@ static void vp_del_vq(struct virtqueue *vq) } static struct virtio_config_ops virtio_pci_config_ops = { - .feature = vp_feature, .get = vp_get, .set = vp_set, .get_status = vp_get_status, @@ -301,6 +299,8 @@ static struct virtio_config_ops virtio_pci_config_ops = { .reset = vp_reset, .find_vq = vp_find_vq, .del_vq = vp_del_vq, + .get_features = vp_get_features, + .set_features = vp_set_features, }; /* the PCI probing function */ -- cgit v1.1