/*
* The virtio core takes the features the Host offers, and copies the ones
* supported by the driver into the vdev->features array. Once that's all
* sorted out, this routine is called so we can tell the Host which features we
* understand and accept.
*/
static void lg_finalize_features(struct virtio_device *vdev)
{
unsigned int i, bits;
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
/* Second half of bitmap is features we accept. */
u8 *out_features = lg_features(desc) + desc->feature_len;
/* Give virtio_ring a chance to accept features. */
vring_transport_features(vdev);
/*
* The vdev->feature array is a Linux bitmask: this isn't the same as a
* the simple array of bits used by lguest devices for features. So we
* do this slow, manual conversion which is completely general.
*/
memset(out_features, 0, desc->feature_len);
bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
for (i = 0; i < bits; i++) {
if (test_bit(i, vdev->features))
out_features[i / 8] |= (1 << (i % 8));
}
/* Tell Host we've finished with this device's feature negotiation */
status_notify(vdev);
}
/* This gets the device's feature bits. */
static u32 lg_get_features(struct virtio_device *vdev)
{
unsigned int i;
u32 features = 0;
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
u8 *in_features = lg_features(desc);
/* We do this the slow but generic way. */
for (i = 0; i < min(desc->feature_len * 8, 32); i++)
if (in_features[i / 8] & (1 << (i % 8)))
features |= (1 << i);
return features;
}
/* This tests (and acknowleges) a feature bit. */
static bool lg_feature(struct virtio_device *vdev, unsigned fbit)
{
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
u8 *features;
/* Obviously if they ask for a feature off the end of our feature
* bitmap, it's not set. */
if (fbit / 8 > desc->feature_len)
return false;
/* The feature bitmap comes after the virtqueues. */
features = lg_features(desc);
if (!(features[fbit / 8] & (1 << (fbit % 8))))
return false;
/* We set the matching bit in the other half of the bitmap to tell the
* Host we want to use this feature. We don't use this yet, but we
* could in future. */
features[desc->feature_len + fbit / 8] |= (1 << (fbit % 8));
return true;
}
/* The config space comes after the two feature bitmasks. */
static u8 *lg_config(const struct lguest_device_desc *desc)
{
return lg_features(desc) + desc->feature_len * 2;
}
