On Fri, Jul 18, 2025 at 10:52:36AM +0200, Paolo Abeni wrote:
Provide extended version of the features manipulation helpers,
and let the device initialization deal with the full features space,
adjusting the relevant format strings accordingly.

Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
v2 -> v3:
 - use virtio_features_andnot return value instead of virtio_features_empty
 - rebased on top of "net: Consolidate vhost feature bits into vhost_net
   structure"
 - _array -> _ex

v1 -> v2:
 - uint128_t -> uint64_t[]
 - provide extended variant of the features manipulation helpers
---
hw/net/vhost_net-stub.c |  8 +++----
hw/net/vhost_net.c      | 46 ++++++++++++++++++++++-------------------
include/net/vhost_net.h | 33 ++++++++++++++++++++++++++---
3 files changed, 58 insertions(+), 29 deletions(-)

diff --git a/hw/net/vhost_net-stub.c b/hw/net/vhost_net-stub.c
index 7d49f82906..0740d5a2eb 100644
--- a/hw/net/vhost_net-stub.c
+++ b/hw/net/vhost_net-stub.c
@@ -46,9 +46,8 @@ void vhost_net_cleanup(struct vhost_net *net)
{
}

-uint64_t vhost_net_get_features(struct vhost_net *net, uint64_t features)
+void vhost_net_get_features_ex(struct vhost_net *net, uint64_t *features)
{
-    return features;
}

int vhost_net_get_config(struct vhost_net *net,  uint8_t *config,
@@ -62,13 +61,12 @@ int vhost_net_set_config(struct vhost_net *net, const 
uint8_t *data,
    return 0;
}

-void vhost_net_ack_features(struct vhost_net *net, uint64_t features)
+void vhost_net_ack_features_ex(struct vhost_net *net, const uint64_t *features)
{
}

-uint64_t vhost_net_get_acked_features(VHostNetState *net)
+void vhost_net_get_acked_features_ex(VHostNetState *net, uint64_t *features)
{
-    return 0;
}

bool vhost_net_virtqueue_pending(VHostNetState *net, int idx)
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 540492b37d..33fc6ba2f9 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -35,10 +35,9 @@
#include "hw/virtio/virtio-bus.h"
#include "linux-headers/linux/vhost.h"

-uint64_t vhost_net_get_features(struct vhost_net *net, uint64_t features)
+void vhost_net_get_features_ex(struct vhost_net *net, uint64_t *features)
{
-    return vhost_get_features(&net->dev, net->feature_bits,
-            features);
+    vhost_get_features_ex(&net->dev, net->feature_bits, features);
}
int vhost_net_get_config(struct vhost_net *net,  uint8_t *config,
                         uint32_t config_len)
@@ -51,10 +50,11 @@ int vhost_net_set_config(struct vhost_net *net, const 
uint8_t *data,
    return vhost_dev_set_config(&net->dev, data, offset, size, flags);
}

-void vhost_net_ack_features(struct vhost_net *net, uint64_t features)
+void vhost_net_ack_features_ex(struct vhost_net *net, const uint64_t *features)
{
-    net->dev.acked_features = net->dev.backend_features;
-    vhost_ack_features(&net->dev, net->feature_bits, features);
+    virtio_features_copy(net->dev.acked_features_ex,
+                         net->dev.backend_features_ex);
+    vhost_ack_features_ex(&net->dev, net->feature_bits, features);
}

uint64_t vhost_net_get_max_queues(VHostNetState *net)
@@ -62,9 +62,9 @@ uint64_t vhost_net_get_max_queues(VHostNetState *net)
    return net->dev.max_queues;
}

-uint64_t vhost_net_get_acked_features(VHostNetState *net)
+void vhost_net_get_acked_features_ex(VHostNetState *net, uint64_t *features)
{
-    return net->dev.acked_features;
+    virtio_features_copy(features, net->dev.acked_features_ex);
}

void vhost_net_save_acked_features(NetClientState *nc)
@@ -234,7 +234,8 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
    int r;
    bool backend_kernel = options->backend_type == VHOST_BACKEND_TYPE_KERNEL;
    struct vhost_net *net = g_new0(struct vhost_net, 1);
-    uint64_t features = 0;
+    uint64_t missing_features[VIRTIO_FEATURES_DWORDS];
+    uint64_t features[VIRTIO_FEATURES_DWORDS];

Should we initialize `features` (IIUC calling virtio_features_clear)
since it was set to 0 before this patch?

    Error *local_err = NULL;

    if (!options->net_backend) {
@@ -261,7 +262,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
        net->backend = r;
        net->dev.protocol_features = 0;
    } else {
-        net->dev.backend_features = 0;
+        virtio_features_clear(net->dev.backend_features_ex);
        net->dev.protocol_features = 0;
        net->backend = -1;

@@ -279,28 +280,31 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
    if (backend_kernel) {
        if (!qemu_has_vnet_hdr_len(options->net_backend,
                               sizeof(struct virtio_net_hdr_mrg_rxbuf))) {
-            net->dev.features &= ~(1ULL << VIRTIO_NET_F_MRG_RXBUF);
+            net->dev.features &= ~VIRTIO_BIT(VIRTIO_NET_F_MRG_RXBUF);
        }
-        if (~net->dev.features & net->dev.backend_features) {
-            fprintf(stderr, "vhost lacks feature mask 0x%" PRIx64
-                   " for backend\n",
-                   (uint64_t)(~net->dev.features & net->dev.backend_features));
+
+        if (virtio_features_andnot(missing_features,
+                                   net->dev.backend_features_ex,
+                                   net->dev.features_ex)) {
+            fprintf(stderr, "vhost lacks feature mask 0x" VIRTIO_FEATURES_FMT
+                   " for backend\n", VIRTIO_FEATURES_PR(missing_features));
            goto fail;
        }
    }

    /* Set sane init value. Override when guest acks. */
    if (options->get_acked_features) {
-        features = options->get_acked_features(net->nc);
-        if (~net->dev.features & features) {
-            fprintf(stderr, "vhost lacks feature mask 0x%" PRIx64
-                    " for backend\n",
-                    (uint64_t)(~net->dev.features & features));
+        virtio_features_from_u64(features,
+                                 options->get_acked_features(net->nc));
+        if (virtio_features_andnot(missing_features, features,
+                                   net->dev.features_ex)) {
+            fprintf(stderr, "vhost lacks feature mask 0x" VIRTIO_FEATURES_FMT
+                    " for backend\n", VIRTIO_FEATURES_PR(missing_features));
            goto fail;
        }
    }

-    vhost_net_ack_features(net, features);
+    vhost_net_ack_features_ex(net, features);

If `options->get_acked_features` is false, `features` here is not
initialized (it was set to 0 before this patch).

Thanks,
Stefano


    return net;

diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index 879781dad7..1d07b437c7 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -2,6 +2,7 @@
#define VHOST_NET_H

#include "net/net.h"
+#include "hw/virtio/virtio-features.h"
#include "hw/virtio/vhost-backend.h"

struct vhost_net;
@@ -33,8 +34,26 @@ void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,

void vhost_net_cleanup(VHostNetState *net);

-uint64_t vhost_net_get_features(VHostNetState *net, uint64_t features);
-void vhost_net_ack_features(VHostNetState *net, uint64_t features);
+void vhost_net_get_features_ex(VHostNetState *net, uint64_t *features);
+static inline uint64_t vhost_net_get_features(VHostNetState *net,
+                                              uint64_t features)
+{
+    uint64_t features_array[VIRTIO_FEATURES_DWORDS];
+
+    virtio_features_from_u64(features_array, features);
+    vhost_net_get_features_ex(net, features_array);
+    return features_array[0];
+}
+
+void vhost_net_ack_features_ex(VHostNetState *net, const uint64_t *features);
+static inline void vhost_net_ack_features(VHostNetState *net,
+                                          uint64_t features)
+{
+    uint64_t features_array[VIRTIO_FEATURES_DWORDS];
+
+    virtio_features_from_u64(features_array, features);
+    vhost_net_ack_features_ex(net, features_array);
+}

int vhost_net_get_config(struct vhost_net *net,  uint8_t *config,
                         uint32_t config_len);
@@ -51,7 +70,15 @@ VHostNetState *get_vhost_net(NetClientState *nc);

int vhost_net_set_vring_enable(NetClientState *nc, int enable);

-uint64_t vhost_net_get_acked_features(VHostNetState *net);
+void vhost_net_get_acked_features_ex(VHostNetState *net, uint64_t *features);
+static inline uint64_t vhost_net_get_acked_features(VHostNetState *net)
+{
+    uint64_t features[VIRTIO_FEATURES_DWORDS];
+
+    vhost_net_get_acked_features_ex(net, features);
+    assert(!virtio_features_use_extended(features));
+    return features[0];
+}

int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu);

--
2.50.0



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