Re: [PATCH net-next v21 05/13] virtio_net: Query and set flow filter caps

On 03/08/2026 18:51, Michael S. Tsirkin wrote:
> On Mon, Aug 03, 2026 at 05:07:13PM +0300, Shahar Shitrit wrote:
>> When probing a virtnet device, attempt to read the flow filter
>> capabilities. In order to use the feature the caps must also
>> be set. For now setting what was read is sufficient.
>>
>> This patch adds uapi definitions virtio_net flow filters define in
>> version 1.4 of the VirtIO spec.
>>
>> Signed-off-by: Daniel Jurgens <[email protected]>
>> Reviewed-by: Parav Pandit <[email protected]>
>> Signed-off-by: Shahar Shitrit <[email protected]>
>> ---
>>  drivers/net/virtio_net.c           | 239 +++++++++++++++++++++++++++++
>>  include/uapi/linux/virtio_net_ff.h |  91 +++++++++++
>>  2 files changed, 330 insertions(+)
>>  create mode 100644 include/uapi/linux/virtio_net_ff.h
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 3e2a5876c6c8..0d1f5a6cfd12 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -27,6 +27,11 @@
>>  #include <net/netdev_queues.h>
>>  #include <net/xdp_sock_drv.h>
>>  #include <net/page_pool/helpers.h>
>> +#include <linux/virtio_admin.h>
>> +#include <net/ipv6.h>
>> +#include <net/ip.h>
>> +#include <uapi/linux/virtio_pci.h>
> 
> why would virtio net need pci macros?
it is not needed. will remove
> 
>> +#include <uapi/linux/virtio_net_ff.h>
>>  
>>  static int napi_weight = NAPI_POLL_WEIGHT;
>>  module_param(napi_weight, int, 0444);
>> @@ -282,6 +287,14 @@ static const struct virtnet_stat_desc virtnet_stats_tx_speed_desc_qstat[] = {
>>  	VIRTNET_STATS_DESC_TX_QSTAT(speed, ratelimit_packets, hw_drop_ratelimits),
>>  };
>>  
>> +struct virtnet_ff {
>> +	struct virtio_device *vdev;
>> +	bool ff_supported;
>> +	struct virtio_net_ff_cap_data *ff_caps;
>> +	struct virtio_net_ff_cap_mask_data *ff_mask;
>> +	struct virtio_net_ff_actions *ff_actions;
>> +};
>> +
>>  #define VIRTNET_Q_TYPE_RX 0
>>  #define VIRTNET_Q_TYPE_TX 1
>>  #define VIRTNET_Q_TYPE_CQ 2
>> @@ -474,6 +487,8 @@ struct virtnet_info {
>>  
>>  	struct virtio_net_rss_config_hdr *rss_hdr;
>>  
>> +	struct virtnet_ff ff;
>> +
>>  	/* Must be last as it ends in a flexible-array member. */
>>  	TRAILING_OVERLAP(struct virtio_net_rss_config_trailer, rss_trailer, hash_key_data,
>>  		u8 rss_hash_key_data[NETDEV_RSS_KEY_LEN];
>> @@ -519,6 +534,7 @@ static struct sk_buff *virtnet_skb_append_frag(struct receive_queue *rq,
>>  static void virtnet_xsk_completed(struct send_queue *sq, int num);
>>  static void free_unused_bufs(struct virtnet_info *vi);
>>  static void virtnet_del_vqs(struct virtnet_info *vi);
>> +static void remove_vq_common(struct virtnet_info *vi);
>>  
>>  enum virtnet_xmit_type {
>>  	VIRTNET_XMIT_TYPE_SKB,
>> @@ -5710,6 +5726,199 @@ static const struct netdev_stat_ops virtnet_stat_ops = {
>>  	.get_base_stats		= virtnet_get_base_stats,
>>  };
>>  
>> +static size_t get_mask_size(u16 type)
>> +{
>> +	switch (type) {
>> +	case VIRTIO_NET_FF_MASK_TYPE_ETH:
>> +		return sizeof(struct ethhdr);
>> +	case VIRTIO_NET_FF_MASK_TYPE_IPV4:
>> +		return sizeof(struct iphdr);
>> +	case VIRTIO_NET_FF_MASK_TYPE_IPV6:
>> +		return sizeof(struct ipv6hdr);
>> +	case VIRTIO_NET_FF_MASK_TYPE_TCP:
>> +		return sizeof(struct tcphdr);
>> +	case VIRTIO_NET_FF_MASK_TYPE_UDP:
>> +		return sizeof(struct udphdr);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int virtnet_ff_init(struct virtnet_ff *ff, struct virtio_device *vdev)
>> +{
>> +	size_t ff_mask_size = sizeof(struct virtio_net_ff_cap_mask_data) +
>> +			      sizeof(struct virtio_net_ff_selector) *
>> +			      VIRTIO_NET_FF_MASK_TYPE_MAX;
>> +	struct virtio_admin_cmd_query_cap_id_result *cap_id_list;
>> +	struct virtio_net_ff_selector *sel;
>> +	unsigned long sel_types = 0;
>> +	size_t real_ff_mask_size;
>> +	int err;
>> +	int i;
>> +
>> +	if (!vdev->config->admin_cmd_exec)
>> +		return -EOPNOTSUPP;
>> +
>> +	cap_id_list = kzalloc(sizeof(*cap_id_list), GFP_KERNEL);
>> +	if (!cap_id_list)
>> +		return -ENOMEM;
>> +
>> +	err = virtio_admin_cap_id_list_query(vdev, cap_id_list);
>> +	if (err)
>> +		goto err_cap_list;
>> +
>> +	if (!(VIRTIO_CAP_IN_LIST(cap_id_list,
>> +				 VIRTIO_NET_FF_RESOURCE_CAP) &&
>> +	      VIRTIO_CAP_IN_LIST(cap_id_list,
>> +				 VIRTIO_NET_FF_SELECTOR_CAP) &&
>> +	      VIRTIO_CAP_IN_LIST(cap_id_list,
>> +				 VIRTIO_NET_FF_ACTION_CAP))) {
>> +		err = -EOPNOTSUPP;
>> +		goto err_cap_list;
>> +	}
>> +
>> +	ff->ff_caps = kzalloc(sizeof(*ff->ff_caps), GFP_KERNEL);
>> +	if (!ff->ff_caps) {
>> +		err = -ENOMEM;
>> +		goto err_cap_list;
>> +	}
>> +
>> +	err = virtio_admin_cap_get(vdev,
>> +				   VIRTIO_NET_FF_RESOURCE_CAP,
>> +				   ff->ff_caps,
>> +				   sizeof(*ff->ff_caps));
>> +
>> +	if (err)
>> +		goto err_ff;
>> +
>> +	if (!le32_to_cpu(ff->ff_caps->groups_limit) ||
>> +	    !le32_to_cpu(ff->ff_caps->classifiers_limit) ||
>> +	    !le32_to_cpu(ff->ff_caps->rules_limit) ||
>> +	    !le32_to_cpu(ff->ff_caps->rules_per_group_limit)) {
> 
> I am not sure why do we validate these specifically.
> 
> Should we then validate selectors_per_classifier_limit too?
there's no special reason. will add a validation for
selectors_per_classifier_limit too
> 
>> +		err = -EINVAL;
>> +		goto err_ff;
>> +	}
>> +
>> +	/* VIRTIO_NET_FF_MASK_TYPE start at 1 */
>> +	for (i = 1; i <= VIRTIO_NET_FF_MASK_TYPE_MAX; i++)
>> +		ff_mask_size += get_mask_size(i);
>> +
>> +	ff->ff_mask = kzalloc(ff_mask_size, GFP_KERNEL);
>> +	if (!ff->ff_mask) {
>> +		err = -ENOMEM;
>> +		goto err_ff;
>> +	}
>> +
>> +	err = virtio_admin_cap_get(vdev,
>> +				   VIRTIO_NET_FF_SELECTOR_CAP,
>> +				   ff->ff_mask,
>> +				   ff_mask_size);
>> +
>> +	if (err)
>> +		goto err_ff_mask;
>> +
>> +	ff->ff_mask->count = min_t(u8, ff->ff_mask->count,
>> +				   VIRTIO_NET_FF_MASK_TYPE_MAX);
>> +
>> +	ff->ff_actions = kzalloc(sizeof(*ff->ff_actions) +
>> +					VIRTIO_NET_FF_ACTION_MAX,
>> +					GFP_KERNEL);
>> +	if (!ff->ff_actions) {
>> +		err = -ENOMEM;
>> +		goto err_ff_mask;
>> +	}
>> +
>> +	err = virtio_admin_cap_get(vdev,
>> +				   VIRTIO_NET_FF_ACTION_CAP,
>> +				   ff->ff_actions,
>> +				   sizeof(*ff->ff_actions) + VIRTIO_NET_FF_ACTION_MAX);
>> +
>> +	if (err)
>> +		goto err_ff_action;
>> +
>> +	ff->ff_actions->count = min_t(u8, ff->ff_actions->count,
>> +				      VIRTIO_NET_FF_ACTION_MAX);
> 
> and here, do we validate count != 0?
will add.
> 
> 
>> +	err = virtio_admin_cap_set(vdev,
>> +				   VIRTIO_NET_FF_RESOURCE_CAP,
>> +				   ff->ff_caps,
>> +				   sizeof(*ff->ff_caps));
>> +	if (err)
>> +		goto err_ff_action;
>> +
>> +	real_ff_mask_size = sizeof(struct virtio_net_ff_cap_mask_data);
>> +	sel = (void *)&ff->ff_mask->selectors;
>> +
>> +	for (i = 0; i < ff->ff_mask->count; i++) {
>> +		/* If the selector type is unknown it may indicate the spec
>> +		 * has been revised to include new types of selectors
>> +		 */
>> +		if (!sel->type || sel->type > VIRTIO_NET_FF_MASK_TYPE_MAX)
>> +			break;
>> +
>> +		if (sel->length != get_mask_size(sel->type) ||
>> +		    test_and_set_bit(sel->type, &sel_types)) {
>> +			WARN_ON_ONCE(true);
> 
> given we gracefully fail, I'm not sure WARN is justified,
> since we don't warn in other validation steps.
> However
> 
> 
>> +			err = -EINVAL;
> 
> 
> the error here is on the device side, not user side, right?
> maybe a distinct error to indicate this.
I remove the WARN_ON_ONCE and replace the -EINVAL with -EPROTO.
> 
>> +			goto err_ff_action;
>> +		}
>> +		real_ff_mask_size += sizeof(*sel) + sel->length;
>> +		if (real_ff_mask_size > ff_mask_size) {
>> +			WARN_ON_ONCE(true);
>> +			err = -EINVAL;
>> +			goto err_ff_action;
>> +		}
>> +		sel = (void *)sel + sizeof(*sel) + sel->length;
>> +	}
>> +	ff->ff_mask->count = i;
>> +
>> +	err = virtio_admin_cap_set(vdev,
>> +				   VIRTIO_NET_FF_SELECTOR_CAP,
>> +				   ff->ff_mask,
>> +				   real_ff_mask_size);
>> +	if (err)
>> +		goto err_ff_action;
>> +
>> +	err = virtio_admin_cap_set(vdev,
>> +				   VIRTIO_NET_FF_ACTION_CAP,
>> +				   ff->ff_actions,
>> +				   sizeof(*ff->ff_actions) + VIRTIO_NET_FF_ACTION_MAX);
> 
> 
> why not ff->ff_mask->count? this is all we initialized...
right
> 
>> +	if (err)
>> +		goto err_ff_action;
>> +
>> +	ff->vdev = vdev;
>> +	ff->ff_supported = true;
>> +
>> +	kfree(cap_id_list);
>> +
>> +	return 0;
>> +
>> +err_ff_action:
>> +	kfree(ff->ff_actions);
>> +	ff->ff_actions = NULL;
>> +err_ff_mask:
>> +	kfree(ff->ff_mask);
>> +	ff->ff_mask = NULL;
>> +err_ff:
>> +	kfree(ff->ff_caps);
>> +	ff->ff_caps = NULL;
>> +err_cap_list:
>> +	kfree(cap_id_list);
>> +
>> +	return err;
>> +}
>> +
>> +static void virtnet_ff_cleanup(struct virtnet_ff *ff)
>> +{
>> +	if (!ff->ff_supported)
>> +		return;
>> +
>> +	kfree(ff->ff_actions);
>> +	kfree(ff->ff_mask);
>> +	kfree(ff->ff_caps);
>> +	ff->ff_supported = false;
>> +}
>> +
>>  static void virtnet_freeze_down(struct virtio_device *vdev)
>>  {
>>  	struct virtnet_info *vi = vdev->priv;
>> @@ -5728,6 +5937,10 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
>>  	netif_tx_lock_bh(vi->dev);
>>  	netif_device_detach(vi->dev);
>>  	netif_tx_unlock_bh(vi->dev);
>> +
>> +	rtnl_lock();
>> +	virtnet_ff_cleanup(&vi->ff);
>> +	rtnl_unlock();
>>  }
>>  
>>  static int init_vqs(struct virtnet_info *vi);
>> @@ -5757,9 +5970,24 @@ static int virtnet_restore_up(struct virtio_device *vdev)
>>  			goto err_destroy_pools;
>>  	}
>>  
>> +	/*
>> +	 * Initialize flow filters. Not supported is an acceptable and common
>> +	 * return code
>> +	 */
>> +	rtnl_lock();
>> +	err = virtnet_ff_init(&vi->ff, vi->vdev);
>> +	if (err && err != -EOPNOTSUPP) {
>> +		rtnl_unlock();
>> +		virtnet_freeze_down(vi->vdev);
>> +		remove_vq_common(vi);
>> +		return err;
>> +	}
>> +	rtnl_unlock();
>> +
>>  	netif_tx_lock_bh(vi->dev);
>>  	netif_device_attach(vi->dev);
>>  	netif_tx_unlock_bh(vi->dev);
>> +
>>  	return 0;
>>  
>>  err_destroy_pools:
>> @@ -7043,6 +7271,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>>  
>>  	virtio_device_ready(vdev);
>>  
>> +	/* Initialize flow filters. Not supported is an acceptable and common
>> +	 * return code
>> +	 */
>> +	err = virtnet_ff_init(&vi->ff, vi->vdev);
>> +	if (err && err != -EOPNOTSUPP) {
>> +		rtnl_unlock();
>> +		goto free_unregister_netdev;
>> +	}
>> +
>>  	if (vi->has_rss || vi->has_rss_hash_report) {
>>  		if (!virtnet_commit_rss_command(vi)) {
>>  			dev_warn(&vdev->dev, "RSS disabled because committing failed.\n");
>> @@ -7125,6 +7362,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>>  
>>  free_unregister_netdev:
>>  	unregister_netdev(dev);
>> +	virtnet_ff_cleanup(&vi->ff);
>>  free_failover:
>>  	net_failover_destroy(vi->failover);
>>  free_page_pools:
>> @@ -7175,6 +7413,7 @@ static void virtnet_remove(struct virtio_device *vdev)
>>  	virtnet_free_irq_moder(vi);
>>  
>>  	unregister_netdev(vi->dev);
>> +	virtnet_ff_cleanup(&vi->ff);
>>  
>>  	net_failover_destroy(vi->failover);
>>  
>> diff --git a/include/uapi/linux/virtio_net_ff.h b/include/uapi/linux/virtio_net_ff.h
>> new file mode 100644
>> index 000000000000..f9e771a0baff
>> --- /dev/null
>> +++ b/include/uapi/linux/virtio_net_ff.h
>> @@ -0,0 +1,91 @@
>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
>> + *
>> + * Header file for virtio_net flow filters
>> + */
>> +#ifndef _LINUX_VIRTIO_NET_FF_H
>> +#define _LINUX_VIRTIO_NET_FF_H
>> +
>> +#include <linux/types.h>
>> +#include <linux/stddef.h>
>> +
>> +#define VIRTIO_NET_FF_RESOURCE_CAP 0x800
>> +#define VIRTIO_NET_FF_SELECTOR_CAP 0x801
>> +#define VIRTIO_NET_FF_ACTION_CAP 0x802
>> +
>> +/**
>> + * struct virtio_net_ff_cap_data - Flow filter resource capability limits
>> + * @groups_limit: maximum number of flow filter groups supported by the device
>> + * @classifiers_limit: maximum number of classifiers supported by the device
>> + * @rules_limit: maximum number of rules supported device-wide across all groups
>> + * @rules_per_group_limit: maximum number of rules allowed in a single group
>> + * @last_rule_priority: priority value associated with the lowest-priority rule
>> + * @selectors_per_classifier_limit: maximum selectors allowed in one classifier
>> + */
>> +struct virtio_net_ff_cap_data {
>> +	__le32 groups_limit;
>> +	__le32 classifiers_limit;
>> +	__le32 rules_limit;
>> +	__le32 rules_per_group_limit;
>> +	__u8 last_rule_priority;
>> +	__u8 selectors_per_classifier_limit;
>> +	/* private: */
>> +	__u8 reserved[2];
>> +};
>> +
>> +/**
>> + * struct virtio_net_ff_selector - Selector mask descriptor
>> + * @type: selector type, one of VIRTIO_NET_FF_MASK_TYPE_* constants
>> + * @flags: selector flags, see VIRTIO_NET_FF_MASK_F_* constants
>> + * @reserved: must be set to 0 by the driver and ignored by the device
>> + * @length: size in bytes of @mask
>> + * @reserved1: must be set to 0 by the driver and ignored by the device
>> + * @mask: variable-length mask payload for @type, length given by @length
>> + *
>> + * A selector describes a header mask that a classifier can apply. The format
>> + * of @mask depends on @type.
>> + */
>> +struct virtio_net_ff_selector {
>> +	__u8 type;
>> +	__u8 flags;
>> +	__u8 reserved[2];
>> +	__u8 length;
>> +	__u8 reserved1[3];
>> +	__u8 mask[] __counted_by(length);
>> +};
>> +
>> +#define VIRTIO_NET_FF_MASK_TYPE_ETH  1
>> +#define VIRTIO_NET_FF_MASK_TYPE_IPV4 2
>> +#define VIRTIO_NET_FF_MASK_TYPE_IPV6 3
>> +#define VIRTIO_NET_FF_MASK_TYPE_TCP  4
>> +#define VIRTIO_NET_FF_MASK_TYPE_UDP  5
>> +#define VIRTIO_NET_FF_MASK_TYPE_MAX  VIRTIO_NET_FF_MASK_TYPE_UDP
>> +
>> +/**
>> + * struct virtio_net_ff_cap_mask_data - Supported selector mask formats
>> + * @count: number of entries in @selectors
>> + * @reserved: must be set to 0 by the driver and ignored by the device
>> + * @selectors: packed array of struct virtio_net_ff_selector.
>> + */
>> +struct virtio_net_ff_cap_mask_data {
>> +	__u8 count;
>> +	__u8 reserved[7];
>> +	__u8 selectors[];
>> +};
>> +
>> +#define VIRTIO_NET_FF_MASK_F_PARTIAL_MASK (1 << 0)
>> +
>> +#define VIRTIO_NET_FF_ACTION_DROP 1
>> +#define VIRTIO_NET_FF_ACTION_RX_VQ 2
>> +#define VIRTIO_NET_FF_ACTION_MAX  VIRTIO_NET_FF_ACTION_RX_VQ
>> +/**
>> + * struct virtio_net_ff_actions - Supported flow actions
>> + * @count: number of supported actions in @actions
>> + * @reserved: must be set to 0 by the driver and ignored by the device
>> + * @actions: array of action identifiers (VIRTIO_NET_FF_ACTION_*)
>> + */
>> +struct virtio_net_ff_actions {
>> +	__u8 count;
>> +	__u8 reserved[7];
>> +	__u8 actions[] __counted_by(count);
>> +};
>> +#endif
>> -- 
>> 2.49.0
>