Re: [PATCH net-next 01/12] ibmvnic: Ensure that subCRQ entry reads are ordered

[drt <drt@linux.vnet.ibm.com>]

On 2020-11-12 11:09, Thomas Falcon wrote:
> Ensure that received Subordinate Command-Response Queue
> entries are properly read in order by the driver.
> 
> Signed-off-by: Thomas Falcon <tlfalcon@linux.ibm.com>

Acked-by: Dany Madden <drt@linux.ibm.com>

> ---
>  drivers/net/ethernet/ibm/ibmvnic.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
> b/drivers/net/ethernet/ibm/ibmvnic.c
> index da15913879f8..5647f54bf387 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -2391,6 +2391,8 @@ static int ibmvnic_poll(struct napi_struct
> *napi, int budget)
> 
>  		if (!pending_scrq(adapter, adapter->rx_scrq[scrq_num]))
>  			break;
> +		/* ensure that we do not prematurely exit the polling loop */
> +		dma_rmb();
>  		next = ibmvnic_next_scrq(adapter, adapter->rx_scrq[scrq_num]);
>  		rx_buff =
>  		    (struct ibmvnic_rx_buff *)be64_to_cpu(next->
> @@ -3087,6 +3089,8 @@ static int ibmvnic_complete_tx(struct
> ibmvnic_adapter *adapter,
>  		int num_entries = 0;
> 
>  		next = ibmvnic_next_scrq(adapter, scrq);
> +		/* ensure that we are reading the correct queue entry */
> +		dma_rmb();
>  		for (i = 0; i < next->tx_comp.num_comps; i++) {
>  			if (next->tx_comp.rcs[i]) {
>  				dev_err(dev, "tx error %x\n",