linux-kernel - Re: [PATCH v3 1/2] vdpa/mlx5: Set speed and duplex of vDPA devices to UNKNOWN

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Message-ID: <f1d671ff-0429-4cb5-a6e8-309a8567924c@nvidia.com>
Date: Fri, 8 Nov 2024 10:31:58 +0100
From: Dragos Tatulea <dtatulea@...dia.com>
To: "Michael S. Tsirkin" <mst@...hat.com>,
 Carlos Bilbao <carlos.bilbao.osdev@...il.com>
Cc: jasowang@...hat.com, shannon.nelson@....com, sashal@...nel.org,
 alvaro.karsz@...id-run.com, christophe.jaillet@...adoo.fr,
 steven.sistare@...cle.com, bilbao@...edu, xuanzhuo@...ux.alibaba.com,
 johnah.palmer@...cle.com, eperezma@...hat.com, cratiu@...dia.com,
 virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Carlos Bilbao <cbilbao@...italocean.com>
Subject: Re: [PATCH v3 1/2] vdpa/mlx5: Set speed and duplex of vDPA devices to
 UNKNOWN



On 07.11.24 22:50, Michael S. Tsirkin wrote:
> On Wed, Sep 04, 2024 at 10:11:14AM -0500, Carlos Bilbao wrote:
>> From: Carlos Bilbao <cbilbao@...italocean.com>
>>
>> Initialize the speed and duplex fields in virtio_net_config to UNKNOWN.
>> This is needed because mlx5_vdpa vDPA devices currently do not support the
>> VIRTIO_NET_F_SPEED_DUPLEX feature which reports speed and duplex.
> 
> I see no logic here. Without this feature bit, guests will not read
> this field, why do we suddenly need to initialize it?
> 
IIRC, Carlos was reading data via ioctl VHOST_VDPA_GET_CONFIG which calls
.get_config() directly, always exposing the speed and duplex config fields [0].
Carlos, was this the case?

[0] https://lore.kernel.org/lkml/afcbf041-7613-48e6-8088-9d52edd907ff@nvidia.com/T/

Thanks,
Dragos

>> Add
>> needed helper cpu_to_mlx5vdpa32() to convert endianness of speed.
>>
>> Signed-off-by: Carlos Bilbao <cbilbao@...italocean.com>
>> Reviewed-by: Dragos Tatulea <dtatulea@...dia.com>
>> ---
>>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> index b56aae3f7be3..41ca268d43ff 100644
>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> @@ -173,6 +173,11 @@ static __virtio16 cpu_to_mlx5vdpa16(struct mlx5_vdpa_dev *mvdev, u16 val)
>>  	return __cpu_to_virtio16(mlx5_vdpa_is_little_endian(mvdev), val);
>>  }
>>  
>> +static __virtio32 cpu_to_mlx5vdpa32(struct mlx5_vdpa_dev *mvdev, u32 val)
>> +{
>> +	return __cpu_to_virtio32(mlx5_vdpa_is_little_endian(mvdev), val);
>> +}
>> +
>>  static u16 ctrl_vq_idx(struct mlx5_vdpa_dev *mvdev)
>>  {
>>  	if (!(mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_MQ)))
>> @@ -3433,6 +3438,13 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
>>  	init_rwsem(&ndev->reslock);
>>  	config = &ndev->config;
>>  
>> +	/*
>> +	 * mlx5_vdpa vDPA devices currently don't support reporting or
>> +	 * setting the speed or duplex.
>> +	 */
>> +	config->speed  = cpu_to_mlx5vdpa32(mvdev, SPEED_UNKNOWN);
>> +	config->duplex = DUPLEX_UNKNOWN;
>> +
>>  	if (add_config->mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU)) {
>>  		err = config_func_mtu(mdev, add_config->net.mtu);
>>  		if (err)
>> -- 
>> 2.34.1
>