Commit d084d996 authored by Si-Wei Liu's avatar Si-Wei Liu Committed by Michael S. Tsirkin
Browse files

vdpa/mlx5: should exclude header length and fcs from mtu 



When feature VIRTIO_NET_F_MTU is negotiated on mlx5_vdpa,
22 extra bytes worth of MTU length is shown in guest.
This is because the mlx5_query_port_max_mtu API returns
the "hardware" MTU value, which does not just contain the
 Ethernet payload, but includes extra lengths starting
from the Ethernet header up to the FCS altogether.

Fix the MTU so packets won't get dropped silently.

Fixes: 1a86b377 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
Signed-off-by: default avatarSi-Wei Liu <si-wei.liu@oracle.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarEli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20210408091047.4269-2-elic@nvidia.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent e49d033b

drivers/vdpa/mlx5/core/mlx5_vdpa.h

+4 −0
Original line number Diff line number Diff line
@@ -4,9 +4,13 @@ 
#ifndef __MLX5_VDPA_H__

#define __MLX5_VDPA_H__



#include <linux/etherdevice.h>

#include <linux/if_vlan.h>

#include <linux/vdpa.h>

#include <linux/mlx5/driver.h>



#define MLX5V_ETH_HARD_MTU (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN)



struct mlx5_vdpa_direct_mr {

	u64 start;

	u64 end;

drivers/vdpa/mlx5/net/mlx5_vnet.c

+14 −1
Original line number Diff line number Diff line
@@ -1907,6 +1907,19 @@ static const struct vdpa_config_ops mlx5_vdpa_ops = { 
	.free = mlx5_vdpa_free,

};



static int query_mtu(struct mlx5_core_dev *mdev, u16 *mtu)

{

	u16 hw_mtu;

	int err;



	err = mlx5_query_nic_vport_mtu(mdev, &hw_mtu);

	if (err)

		return err;



	*mtu = hw_mtu - MLX5V_ETH_HARD_MTU;

	return 0;

}



static int alloc_resources(struct mlx5_vdpa_net *ndev)

{

	struct mlx5_vdpa_net_resources *res = &ndev->res;
@@ -1992,7 +2005,7 @@ static int mlx5v_probe(struct auxiliary_device *adev, 
	init_mvqs(ndev);

	mutex_init(&ndev->reslock);

	config = &ndev->config;

	err = mlx5_query_nic_vport_mtu(mdev, &ndev->mtu);

	err = query_mtu(mdev, &ndev->mtu);

	if (err)

		goto err_mtu;