netdev - Re: [PATCH net 1/1] ixgbe: Add locking to prevent panic when setting sriov

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Date:   Fri, 13 Aug 2021 17:20:33 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>
Cc:     davem@...emloft.net, Ken Cox <jkc@...hat.com>,
        netdev@...r.kernel.org,
        Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>,
        Marek Szlosek <marek.szlosek@...el.com>
Subject: Re: [PATCH net 1/1] ixgbe: Add locking to prevent panic when
 setting sriov_numvfs to zero

On Thu, 12 Aug 2021 10:18:56 -0700 Tony Nguyen wrote:
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
> index 214a38de3f41..0a1a8756f1fd 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
> @@ -206,8 +206,12 @@ int ixgbe_disable_sriov(struct ixgbe_adapter *adapter)
>  	unsigned int num_vfs = adapter->num_vfs, vf;
>  	int rss;
>  
> +	while (test_and_set_bit(__IXGBE_DISABLING_VFS, &adapter->state))
> +		usleep_range(1000, 2000);
> +
>  	/* set num VFs to 0 to prevent access to vfinfo */
>  	adapter->num_vfs = 0;
> +	clear_bit(__IXGBE_DISABLING_VFS, &adapter->state);
>  
>  	/* put the reference to all of the vf devices */
>  	for (vf = 0; vf < num_vfs; ++vf) {
> @@ -1307,6 +1311,9 @@ void ixgbe_msg_task(struct ixgbe_adapter *adapter)
>  	struct ixgbe_hw *hw = &adapter->hw;
>  	u32 vf;
>  
> +	if (test_and_set_bit(__IXGBE_DISABLING_VFS, &adapter->state))
> +		return;
> +
>  	for (vf = 0; vf < adapter->num_vfs; vf++) {
>  		/* process any reset requests */
>  		if (!ixgbe_check_for_rst(hw, vf))
> @@ -1320,6 +1327,7 @@ void ixgbe_msg_task(struct ixgbe_adapter *adapter)
>  		if (!ixgbe_check_for_ack(hw, vf))
>  			ixgbe_rcv_ack_from_vf(adapter, vf);
>  	}
> +	clear_bit(__IXGBE_DISABLING_VFS, &adapter->state);

Like I've already said two or three times. No flag based locking.