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virtio: add support for negotiating extended features

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The virtio specifications allows for a device features space up
to 128 bits and more. Soon we are going to use some of the 'extended'
bits features for the virtio net driver.

Add support to allow extended features negotiation on a per
devices basis. Devices willing to negotiated extended features
need to implemented a new pair of features getter/setter, the
core will conditionally use them instead of the basic one.

Note that 'bad_features' don't need to be extended, as they are
bound to the 64 bits limit.

Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <9bb29d70adc3f2b8c7756d4e3cd076cffee87826.1758549625.git.pabeni@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Paolo Abeni 2025-09-22 16:18:20 +02:00 • committed by Michael S. Tsirkin
parent 0a49a97433
commit 64a6a336f4
3 changed files with 23 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

11
hw/virtio/virtio-bus.c
View file

@ -62,9 +62,14 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp)
}
/* Get the features of the plugged device. */
assert(vdc->get_features != NULL);
vdev->host_features = vdc->get_features(vdev, vdev->host_features,
&local_err);
if (vdc->get_features_ex) {
vdc->get_features_ex(vdev, vdev->host_features_ex, &local_err);
} else {
assert(vdc->get_features != NULL);
virtio_features_from_u64(vdev->host_features_ex,
vdc->get_features(vdev, vdev->host_features,
&local_err));
}
if (local_err) {
error_propagate(errp, local_err);
return;

14
hw/virtio/virtio.c
View file

@ -3103,7 +3103,9 @@ static int virtio_set_features_nocheck(VirtIODevice *vdev, const uint64_t *val)
bad = virtio_features_andnot(tmp, val, vdev->host_features_ex);
virtio_features_and(tmp, val, vdev->host_features_ex);
if (k->set_features) {
if (k->set_features_ex) {
k->set_features_ex(vdev, val);
} else if (k->set_features) {
bad = bad || virtio_features_use_ex(tmp);
k->set_features(vdev, tmp[0]);
}
@ -3149,6 +3151,13 @@ virtio_set_features_nocheck_maybe_co(VirtIODevice *vdev,
int virtio_set_features(VirtIODevice *vdev, uint64_t val)
{
uint64_t features[VIRTIO_FEATURES_NU64S];
virtio_features_from_u64(features, val);
return virtio_set_features_ex(vdev, features);
}
int virtio_set_features_ex(VirtIODevice *vdev, const uint64_t *features)
{
int ret;
/*
* The driver must not attempt to set features after feature negotiation
@ -3158,13 +3167,12 @@ int virtio_set_features(VirtIODevice *vdev, uint64_t val)
return -EINVAL;
}
if (val & (1ull << VIRTIO_F_BAD_FEATURE)) {
if (features[0] & (1ull << VIRTIO_F_BAD_FEATURE)) {
qemu_log_mask(LOG_GUEST_ERROR,
"%s: guest driver for %s has enabled UNUSED(30) feature bit!\n",
__func__, vdev->name);
}
virtio_features_from_u64(features, val);
ret = virtio_set_features_nocheck(vdev, features);
if (virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
/* VIRTIO_RING_F_EVENT_IDX changes the size of the caches. */

4
include/hw/virtio/virtio.h
View file

@ -178,6 +178,9 @@ struct VirtioDeviceClass {
/* This is what a VirtioDevice must implement */
DeviceRealize realize;
DeviceUnrealize unrealize;
void (*get_features_ex)(VirtIODevice *vdev, uint64_t *requested_features,
Error **errp);
void (*set_features_ex)(VirtIODevice *vdev, const uint64_t *val);
uint64_t (*get_features)(VirtIODevice *vdev,
uint64_t requested_features,
Error **errp);
@ -373,6 +376,7 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index);
void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
void virtio_update_irq(VirtIODevice *vdev);
int virtio_set_features(VirtIODevice *vdev, uint64_t val);
int virtio_set_features_ex(VirtIODevice *vdev, const uint64_t *val);
/* Base devices. */
typedef struct VirtIOBlkConf VirtIOBlkConf;