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Message-ID: <f714fc53-a9a0-4c4d-bd94-f895ddfc972c@daynix.com>
Date: Wed, 19 Mar 2025 13:43:22 +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 2025/03/17 10:15, Jason Wang wrote:
> On Wed, Mar 12, 2025 at 1:59 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>
>> On 2025/03/12 12:36, Jason Wang wrote:
>>> On Tue, Mar 11, 2025 at 2:24 PM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
>>>>
>>>> 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.
>>>
>>> I meant this part.
>>>
>>>>>>> + if (copy_to_iter(&hdr, vhost_hlen,
>>>>>>> + &fixup) != vhost_hlen) {
>>>
>>> We should copy only sizeof(hdr) instead of vhost_hlen.> > Anything I miss?
>>
>> sizeof(hdr) will be greater than vhost_hlen when neither
>> VIRTIO_NET_F_MRG_RXBUF or VIRTIO_F_VERSION_1 is negotiated.
>
> Just to make sure we are on the same page I meant we should only
> advance sizeof(struct virtio_net_hdr) here to make sure we can set the
> num_buffers correctly.
>
> But this is not what the code did here.
This code wrote num_buffers in hdr instead of setting it later.
However, with v10, I changed it again to fill the whole header with zero
and to set num_buffers later. The end result is identical either way;
num_buffers has the correct value and the other fields are filled with zero.
Regards,
Akihiko Odaki
>
> Thanks
>
>>
>> Regards,
>> Akihiko Odaki
>>
>>>
>>> Thanks
>>>
>>>>
>>>> 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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