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Message-ID: <1dd2417a-3246-44b0-b4ba-feadfd6f794e@daynix.com>
Date: Tue, 11 Mar 2025 15:24:06 +0900
From: Akihiko Odaki <akihiko.odaki@...nix.com>
To: Jason Wang <jasowang@...hat.com>
Cc: Jonathan Corbet <corbet@....net>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>, Xuan Zhuo
<xuanzhuo@...ux.alibaba.com>, Shuah Khan <shuah@...nel.org>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org,
Yuri Benditovich <yuri.benditovich@...nix.com>,
Andrew Melnychenko <andrew@...nix.com>,
Stephen Hemminger <stephen@...workplumber.org>, gur.stavi@...wei.com,
Lei Yang <leiyang@...hat.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next v9 6/6] vhost/net: Support
VIRTIO_NET_F_HASH_REPORT
On 2025/03/11 9:42, Jason Wang wrote:
> On Mon, Mar 10, 2025 at 3:04 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>
>> On 2025/03/10 13:43, Jason Wang wrote:
>>> On Fri, Mar 7, 2025 at 7:02 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>>>
>>>> VIRTIO_NET_F_HASH_REPORT allows to report hash values calculated on the
>>>> host. When VHOST_NET_F_VIRTIO_NET_HDR is employed, it will report no
>>>> hash values (i.e., the hash_report member is always set to
>>>> VIRTIO_NET_HASH_REPORT_NONE). Otherwise, the values reported by the
>>>> underlying socket will be reported.
>>>>
>>>> VIRTIO_NET_F_HASH_REPORT requires VIRTIO_F_VERSION_1.
>>>>
>>>> Signed-off-by: Akihiko Odaki <akihiko.odaki@...nix.com>
>>>> Tested-by: Lei Yang <leiyang@...hat.com>
>>>> ---
>>>> drivers/vhost/net.c | 49 +++++++++++++++++++++++++++++--------------------
>>>> 1 file changed, 29 insertions(+), 20 deletions(-)
>>>>
>>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>>> index b9b9e9d40951856d881d77ac74331d914473cd56..16b241b44f89820a42c302f3586ea6bb5e0d4289 100644
>>>> --- a/drivers/vhost/net.c
>>>> +++ b/drivers/vhost/net.c
>>>> @@ -73,6 +73,7 @@ enum {
>>>> VHOST_NET_FEATURES = VHOST_FEATURES |
>>>> (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
>>>> (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
>>>> + (1ULL << VIRTIO_NET_F_HASH_REPORT) |
>>>> (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
>>>> (1ULL << VIRTIO_F_RING_RESET)
>>>> };
>>>> @@ -1097,9 +1098,11 @@ static void handle_rx(struct vhost_net *net)
>>>> .msg_controllen = 0,
>>>> .msg_flags = MSG_DONTWAIT,
>>>> };
>>>> - struct virtio_net_hdr hdr = {
>>>> - .flags = 0,
>>>> - .gso_type = VIRTIO_NET_HDR_GSO_NONE
>>>> + struct virtio_net_hdr_v1_hash hdr = {
>>>> + .hdr = {
>>>> + .flags = 0,
>>>> + .gso_type = VIRTIO_NET_HDR_GSO_NONE
>>>> + }
>>>> };
>>>> size_t total_len = 0;
>>>> int err, mergeable;
>>>> @@ -1110,7 +1113,6 @@ static void handle_rx(struct vhost_net *net)
>>>> bool set_num_buffers;
>>>> struct socket *sock;
>>>> struct iov_iter fixup;
>>>> - __virtio16 num_buffers;
>>>> int recv_pkts = 0;
>>>>
>>>> mutex_lock_nested(&vq->mutex, VHOST_NET_VQ_RX);
>>>> @@ -1191,30 +1193,30 @@ static void handle_rx(struct vhost_net *net)
>>>> vhost_discard_vq_desc(vq, headcount);
>>>> continue;
>>>> }
>>>> + hdr.hdr.num_buffers = cpu_to_vhost16(vq, headcount);
>>>> /* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
>>>> if (unlikely(vhost_hlen)) {
>>>> - if (copy_to_iter(&hdr, sizeof(hdr),
>>>> - &fixup) != sizeof(hdr)) {
>>>> + if (copy_to_iter(&hdr, vhost_hlen,
>>>> + &fixup) != vhost_hlen) {
>>>> vq_err(vq, "Unable to write vnet_hdr "
>>>> "at addr %p\n", vq->iov->iov_base);
>>>> goto out;
>>>
>>> Is this an "issue" specific to RSS/HASH? If it's not, we need a separate patch.
>>>
>>> Honestly, I'm not sure if it's too late to fix this.
>>
>> There is nothing wrong with the current implementation.
>
> Note that I meant the vhost_hlen part, and the current code is tricky.
>
> The comment said:
>
> """
> /* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
> """
>
> So it tries to only offer virtio_net_hdr even if vhost_hlen is the set
> to mrg_rxbuf len.
>
> And this patch changes this behaviour.
mrg_rxbuf only adds the num_buffers field, which is always set for
mrg_rxbuf.
The num_buffers was not set for VIRTIO_F_VERSION_1 in the past, but this
was also fixed with commit a3b9c053d82a ("vhost/net: Set num_buffers for
virtio 1.0")
So there is no behavioral change for existing features with this patch.
Regards,
Akihiko Odaki
>
> Thanks
>
>> The current
>> implementation fills the header with zero except num_buffers, which it
>> fills some real value. This functionality is working fine with
>> VIRTIO_NET_F_MRG_RXBUF and VIRTIO_F_VERSION_1, which change the header size.
>>
>> Now I'm adding VIRTIO_NET_F_HASH_REPORT and it adds the hash_report
>> field, which also needs to be initialized with zero, so I'm making sure
>> vhost_net will also initialize it.
>>
>> Regards,
>> Akihiko Odaki
>>
>>>
>>> Others look fine.
>>>
>>> Thanks
>>>
>>
>
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