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

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Message-ID: <20241108065046-mutt-send-email-mst@kernel.org>
Date: Fri, 8 Nov 2024 06:51:43 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: Carlos Bilbao <carlos.bilbao.osdev@...il.com>, 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 Fri, Nov 08, 2024 at 10:31:58AM +0100, Dragos Tatulea wrote:
> 
> 
> 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

Basically, driver should ignore these if feature is not set.


> >> 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
> >