RE: [PATCH iwl-net] ixgbevf: add missing negotiate_features op to Hyper-V ops table

[Loktionov, Aleksandr]

> -----Original Message-----
> From: Michal Schmidt <mschmidt@xxxxxxxxxx>
> Sent: Friday, March 13, 2026 9:22 AM
> To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel,
> Przemyslaw <przemyslaw.kitszel@xxxxxxxxx>; Andrew Lunn
> <andrew+netdev@xxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric
> Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo
> Abeni <pabeni@xxxxxxxxxx>; Keller, Jacob E <jacob.e.keller@xxxxxxxxx>;
> Loktionov, Aleksandr <aleksandr.loktionov@xxxxxxxxx>; Jagielski,
> Jedrzej <jedrzej.jagielski@xxxxxxxxx>
> Cc: Xiaoqiang Xiong <xxiong@xxxxxxxxxx>; intel-wired-
> lan@xxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH iwl-net] ixgbevf: add missing negotiate_features op to
> Hyper-V ops table
> 
> Commit a7075f501bd3 ("ixgbevf: fix mailbox API compatibility by
> negotiating supported features") added the .negotiate_features
> callback to ixgbe_mac_operations and populated it in ixgbevf_mac_ops,
> but forgot to add it to ixgbevf_hv_mac_ops. This leaves the function
> pointer NULL on Hyper-V VMs.
> 
> During probe, ixgbevf_negotiate_api() calls ixgbevf_set_features(),
> which unconditionally dereferences hw->mac.ops.negotiate_features().
> On Hyper-V this results in a NULL pointer dereference:
> 
>   BUG: kernel NULL pointer dereference, address: 0000000000000000
>   [...]
>   Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine
> [...]
>   Workqueue: events work_for_cpu_fn
>   RIP: 0010:0x0
>   [...]
>   Call Trace:
>    ixgbevf_negotiate_api+0x66/0x160 [ixgbevf]
>    ixgbevf_sw_init+0xe4/0x1f0 [ixgbevf]
>    ixgbevf_probe+0x20f/0x4a0 [ixgbevf]
>    local_pci_probe+0x50/0xa0
>    work_for_cpu_fn+0x1a/0x30
>    [...]
> 
> Add ixgbevf_hv_negotiate_features_vf() that returns -EOPNOTSUPP and
> wire it into ixgbevf_hv_mac_ops. The caller already handles -
> EOPNOTSUPP gracefully.
> 
> Fixes: a7075f501bd3 ("ixgbevf: fix mailbox API compatibility by
> negotiating supported features")
> Reported-by: Xiaoqiang Xiong <xxiong@xxxxxxxxxx>
> Closes: https://issues.redhat.com/browse/RHEL-155455
> Assisted-by: Claude:claude-4.6-opus-high Cursor
> Tested-by: Xiaoqiang Xiong <xxiong@xxxxxxxxxx>
> Signed-off-by: Michal Schmidt <mschmidt@xxxxxxxxxx>
> ---
>  drivers/net/ethernet/intel/ixgbevf/vf.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.c
> b/drivers/net/ethernet/intel/ixgbevf/vf.c
> index b67b580f7f1c..f6df86d124b9 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/vf.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/vf.c
> @@ -709,6 +709,12 @@ static int ixgbevf_negotiate_features_vf(struct
> ixgbe_hw *hw, u32 *pf_features)
>  	return err;
>  }
> 
> +static int ixgbevf_hv_negotiate_features_vf(struct ixgbe_hw *hw,
> +					    u32 *pf_features)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  /**
>   *  ixgbevf_set_vfta_vf - Set/Unset VLAN filter table address
>   *  @hw: pointer to the HW structure
> @@ -1142,6 +1148,7 @@ static const struct ixgbe_mac_operations
> ixgbevf_hv_mac_ops = {
>  	.setup_link		= ixgbevf_setup_mac_link_vf,
>  	.check_link		= ixgbevf_hv_check_mac_link_vf,
>  	.negotiate_api_version	=
> ixgbevf_hv_negotiate_api_version_vf,
> +	.negotiate_features	= ixgbevf_hv_negotiate_features_vf,
>  	.set_rar		= ixgbevf_hv_set_rar_vf,
>  	.update_mc_addr_list	= ixgbevf_hv_update_mc_addr_list_vf,
>  	.update_xcast_mode	= ixgbevf_hv_update_xcast_mode,
> --
> 2.53.0

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>