Hello, On 11/8/24 5:51 AM, Michael S. Tsirkin wrote: > 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@xxxxxxxxxxxxxxxx> >>>> >>>> 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@xxxxxxxxxx/T/ >> >> Thanks, >> Dragos > Basically, driver should ignore these if feature is not set. There _is_ a chance the guest could read this field; As Dragos mentioned, I was using the VHOST_VDPA_GET_CONFIG ioctl from userspace, and the incorrect field initialization led me to believe I was in half-duplex mode -- something people told me they hadn't seen since the 80s. But as Andrew (CCed) mentioned, "If the speed is 0, does duplex even matter?". I also tried to remove the pointless ioctl call altogether to avoid further confusion [0] but that wasn't viable due to spec compliance. Initializing the fields seems the simple solution here (and, IMHO, more generally, it's as a good programming practice) Thanks for looking into this! Best, Carlos [0] https://lore.kernel.org/lkml/CACGkMEvfdUYLjx-Z+oB11XW-54ErJsQMKcnu2p=dsj5N_BiEKw@xxxxxxxxxxxxxx/ > > >>>> Add >>>> needed helper cpu_to_mlx5vdpa32() to convert endianness of speed. >>>> >>>> Signed-off-by: Carlos Bilbao <cbilbao@xxxxxxxxxxxxxxxx> >>>> Reviewed-by: Dragos Tatulea <dtatulea@xxxxxxxxxx> >>>> --- >>>> 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
