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Message-ID: <764ca4a4-3587-4dd4-93a4-23542b32dbf9@daynix.com>
Date: Fri, 21 Mar 2025 15:34:50 +0900
From: Akihiko Odaki <akihiko.odaki@...nix.com>
To: Jason Wang <jasowang@...hat.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
<eperezma@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Andrew Melnychenko <andrew@...nix.com>, Joe Damato <jdamato@...tly.com>,
Philo Lu <lulie@...ux.alibaba.com>, virtualization@...ts.linux.dev,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org, devel@...nix.com
Subject: Re: [PATCH net-next 3/4] virtio_net: Use new RSS config structs
On 2025/03/21 9:35, Jason Wang wrote:
> On Thu, Mar 20, 2025 at 1:36 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>
>> On 2025/03/20 10:50, Jason Wang wrote:
>>> On Wed, Mar 19, 2025 at 12:48 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>>>
>>>> On 2025/03/19 10:43, Jason Wang wrote:
>>>>> On Tue, Mar 18, 2025 at 5:57 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>>>>>
>>>>>> The new RSS configuration structures allow easily constructing data for
>>>>>> VIRTIO_NET_CTRL_MQ_RSS_CONFIG as they strictly follow the order of data
>>>>>> for the command.
>>>>>>
>>>>>> Signed-off-by: Akihiko Odaki <akihiko.odaki@...nix.com>
>>>>>> ---
>>>>>> drivers/net/virtio_net.c | 117 +++++++++++++++++------------------------------
>>>>>> 1 file changed, 43 insertions(+), 74 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>>>>> index d1ed544ba03a..4153a0a5f278 100644
>>>>>> --- a/drivers/net/virtio_net.c
>>>>>> +++ b/drivers/net/virtio_net.c
>>>>>> @@ -360,24 +360,7 @@ struct receive_queue {
>>>>>> struct xdp_buff **xsk_buffs;
>>>>>> };
>>>>>>
>>>>>> -/* This structure can contain rss message with maximum settings for indirection table and keysize
>>>>>> - * Note, that default structure that describes RSS configuration virtio_net_rss_config
>>>>>> - * contains same info but can't handle table values.
>>>>>> - * In any case, structure would be passed to virtio hw through sg_buf split by parts
>>>>>> - * because table sizes may be differ according to the device configuration.
>>>>>> - */
>>>>>> #define VIRTIO_NET_RSS_MAX_KEY_SIZE 40
>>>>>> -struct virtio_net_ctrl_rss {
>>>>>> - __le32 hash_types;
>>>>>> - __le16 indirection_table_mask;
>>>>>> - __le16 unclassified_queue;
>>>>>> - __le16 hash_cfg_reserved; /* for HASH_CONFIG (see virtio_net_hash_config for details) */
>>>>>> - __le16 max_tx_vq;
>>>>>> - u8 hash_key_length;
>>>>>> - u8 key[VIRTIO_NET_RSS_MAX_KEY_SIZE];
>>>>>> -
>>>>>> - __le16 *indirection_table;
>>>>>> -};
>>>>>>
>>>>>> /* Control VQ buffers: protected by the rtnl lock */
>>>>>> struct control_buf {
>>>>>> @@ -421,7 +404,9 @@ struct virtnet_info {
>>>>>> u16 rss_indir_table_size;
>>>>>> u32 rss_hash_types_supported;
>>>>>> u32 rss_hash_types_saved;
>>>>>> - struct virtio_net_ctrl_rss rss;
>>>>>> + struct virtio_net_rss_config_hdr *rss_hdr;
>>>>>> + struct virtio_net_rss_config_trailer rss_trailer;
>>>>>> + u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
>>>>>>
>>>>>> /* Has control virtqueue */
>>>>>> bool has_cvq;
>>>>>> @@ -523,23 +508,16 @@ enum virtnet_xmit_type {
>>>>>> VIRTNET_XMIT_TYPE_XSK,
>>>>>> };
>>>>>>
>>>>>> -static int rss_indirection_table_alloc(struct virtio_net_ctrl_rss *rss, u16 indir_table_size)
>>>>>> +static size_t virtnet_rss_hdr_size(const struct virtnet_info *vi)
>>>>>> {
>>>>>> - if (!indir_table_size) {
>>>>>> - rss->indirection_table = NULL;
>>>>>> - return 0;
>>>>>> - }
>>>>>> + u16 indir_table_size = vi->has_rss ? vi->rss_indir_table_size : 1;
>>>>>>
>>>>>> - rss->indirection_table = kmalloc_array(indir_table_size, sizeof(u16), GFP_KERNEL);
>>>>>> - if (!rss->indirection_table)
>>>>>> - return -ENOMEM;
>>>>>> -
>>>>>> - return 0;
>>>>>> + return struct_size(vi->rss_hdr, indirection_table, indir_table_size);
>>>>>> }
>>>>>>
>>>>>> -static void rss_indirection_table_free(struct virtio_net_ctrl_rss *rss)
>>>>>> +static size_t virtnet_rss_trailer_size(const struct virtnet_info *vi)
>>>>>> {
>>>>>> - kfree(rss->indirection_table);
>>>>>> + return struct_size(&vi->rss_trailer, hash_key_data, vi->rss_key_size);
>>>>>> }
>>>>>>
>>>>>> /* We use the last two bits of the pointer to distinguish the xmit type. */
>>>>>> @@ -3576,15 +3554,16 @@ static void virtnet_rss_update_by_qpairs(struct virtnet_info *vi, u16 queue_pair
>>>>>>
>>>>>> for (; i < vi->rss_indir_table_size; ++i) {
>>>>>> indir_val = ethtool_rxfh_indir_default(i, queue_pairs);
>>>>>> - vi->rss.indirection_table[i] = cpu_to_le16(indir_val);
>>>>>> + vi->rss_hdr->indirection_table[i] = cpu_to_le16(indir_val);
>>>>>> }
>>>>>> - vi->rss.max_tx_vq = cpu_to_le16(queue_pairs);
>>>>>> + vi->rss_trailer.max_tx_vq = cpu_to_le16(queue_pairs);
>>>>>> }
>>>>>>
>>>>>> static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
>>>>>> {
>>>>>> struct virtio_net_ctrl_mq *mq __free(kfree) = NULL;
>>>>>> - struct virtio_net_ctrl_rss old_rss;
>>>>>> + struct virtio_net_rss_config_hdr *old_rss_hdr;
>>>>>> + struct virtio_net_rss_config_trailer old_rss_trailer;
>>>>>> struct net_device *dev = vi->dev;
>>>>>> struct scatterlist sg;
>>>>>>
>>>>>> @@ -3599,24 +3578,28 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
>>>>>> * update (VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET below) and return directly.
>>>>>> */
>>>>>> if (vi->has_rss && !netif_is_rxfh_configured(dev)) {
>>>>>> - memcpy(&old_rss, &vi->rss, sizeof(old_rss));
>>>>>> - if (rss_indirection_table_alloc(&vi->rss, vi->rss_indir_table_size)) {
>>>>>> - vi->rss.indirection_table = old_rss.indirection_table;
>>>>>> + old_rss_hdr = vi->rss_hdr;
>>>>>> + old_rss_trailer = vi->rss_trailer;
>>>>>> + vi->rss_hdr = kmalloc(virtnet_rss_hdr_size(vi), GFP_KERNEL);
>>>>>> + if (!vi->rss_hdr) {
>>>>>> + vi->rss_hdr = old_rss_hdr;
>>>>>> return -ENOMEM;
>>>>>> }
>>>>>>
>>>>>> + *vi->rss_hdr = *old_rss_hdr;
>>>>>> virtnet_rss_update_by_qpairs(vi, queue_pairs);
>>>>>>
>>>>>> if (!virtnet_commit_rss_command(vi)) {
>>>>>> /* restore ctrl_rss if commit_rss_command failed */
>>>>>> - rss_indirection_table_free(&vi->rss);
>>>>>> - memcpy(&vi->rss, &old_rss, sizeof(old_rss));
>>>>>> + kfree(vi->rss_hdr);
>>>>>> + vi->rss_hdr = old_rss_hdr;
>>>>>> + vi->rss_trailer = old_rss_trailer;
>>>>>>
>>>>>> dev_warn(&dev->dev, "Fail to set num of queue pairs to %d, because committing RSS failed\n",
>>>>>> queue_pairs);
>>>>>> return -EINVAL;
>>>>>> }
>>>>>> - rss_indirection_table_free(&old_rss);
>>>>>> + kfree(old_rss_hdr);
>>>>>> goto succ;
>>>>>> }
>>>>>>
>>>>>> @@ -4059,28 +4042,12 @@ static int virtnet_set_ringparam(struct net_device *dev,
>>>>>> static bool virtnet_commit_rss_command(struct virtnet_info *vi)
>>>>>> {
>>>>>> struct net_device *dev = vi->dev;
>>>>>> - struct scatterlist sgs[4];
>>>>>> - unsigned int sg_buf_size;
>>>>>> + struct scatterlist sgs[2];
>>>>>>
>>>>>> /* prepare sgs */
>>>>>> - sg_init_table(sgs, 4);
>>>>>> -
>>>>>> - sg_buf_size = offsetof(struct virtio_net_ctrl_rss, hash_cfg_reserved);
>>>>>> - sg_set_buf(&sgs[0], &vi->rss, sg_buf_size);
>>>>>> -
>>>>>> - if (vi->has_rss) {
>>>>>> - sg_buf_size = sizeof(uint16_t) * vi->rss_indir_table_size;
>>>>>> - sg_set_buf(&sgs[1], vi->rss.indirection_table, sg_buf_size);
>>>>>> - } else {
>>>>>> - sg_set_buf(&sgs[1], &vi->rss.hash_cfg_reserved, sizeof(uint16_t));
>>>>>> - }
>>>>>> -
>>>>>> - sg_buf_size = offsetof(struct virtio_net_ctrl_rss, key)
>>>>>> - - offsetof(struct virtio_net_ctrl_rss, max_tx_vq);
>>>>>> - sg_set_buf(&sgs[2], &vi->rss.max_tx_vq, sg_buf_size);
>>>>>> -
>>>>>> - sg_buf_size = vi->rss_key_size;
>>>>>> - sg_set_buf(&sgs[3], vi->rss.key, sg_buf_size);
>>>>>> + sg_init_table(sgs, 2);
>>>>>> + sg_set_buf(&sgs[0], vi->rss_hdr, virtnet_rss_hdr_size(vi));
>>>>>> + sg_set_buf(&sgs[1], &vi->rss_trailer, virtnet_rss_trailer_size(vi));
>>>>>
>>>>> So I still see this:
>>>>>
>>>>> if (vi->has_rss || vi->has_rss_hash_report) {
>>>>> if (!virtnet_commit_rss_command(vi)) {
>>>>>
>>>>> Should we introduce a hash config helper instead?
>>>>
>>>> I think it's fine to use virtnet_commit_rss_command() for hash
>>>> reporting. struct virtio_net_hash_config and struct
>>>> virtio_net_rss_config are defined to have a common layout to allow
>>>> sharing this kind of logic.
>>>
>>> Well, this trick won't work if the reserved field in hash_config is
>>> used in the future.
>>
>> Right, but we can add a hash config helper when that happens. It will
>> only result in a duplication of logic for now.
>>
>> Regards,
>> Akihiko Odaki
>
> That's tricky as the cvq commands were designed to be used separately.
> Let's use a separate helper and virtio_net_hash_config uAPIs now.
It's not tricky but is explicitly stated in the spec. 5.1.6.5.6.4 "Hash
calculation" says:
> Field reserved MUST contain zeroes. It is defined to make the
> structure to match the layout of virtio_net_rss_config structure,
> defined in 5.1.6.5.7.
By the way, I found it says field reserved MUST contain zeros but we do
nothing to ensure that. I'll write a fix for that.
Regards,
Akihiko Odaki
>
> Thanks
>
>>
>>>
>>> Thanks
>>>
>>>>
>>>> Regards,
>>>> Akihiko Odaki
>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>
>>>
>>
>
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