On Fri, Sep 12, 2025 at 03:06:57PM +0200, Paolo Abeni wrote:
The virtio specifications allows for up to 128 bits for the
I'm not really sure about this, IIUC the spec doesn't set any upper
limit. From
https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.html#x1-140002
2.2 Feature Bits
...
42 to 49, and 128 and above
Feature bits reserved for future extensions.
BTW I don't think that's a valid reason to re-post this series. Let's
only fix it if we have to re-send it for other reason.
Acked-by: Stefano Garzarella <[email protected]>
device features. 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 <[email protected]>
Acked-by: Jason Wang <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>
---
v4 -> v5:
- reordered virtio_set_features{_ex}() definitions
v3 -> v4:
- use new virtio_features macro names
v2 -> v3:
- _array -> _ex
v1 -> v2:
- uint128_t -> uint64_t[]
---
hw/virtio/virtio-bus.c | 11 ++++++++---
hw/virtio/virtio.c | 14 +++++++++++---
include/hw/virtio/virtio.h | 4 ++++
3 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 11adfbf3ab..cef944e015 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -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;
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index bf53c211e5..34f977a3c9 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -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. */
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 39e4059a66..2aeb021fb3 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -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;
--
2.51.0
