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

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Message-ID: <527f42fa5e6a087101cbc19934611783@linux.vnet.ibm.com>
Date:   Thu, 12 Nov 2020 21:45:52 -0800
From:   drt <drt@...ux.vnet.ibm.com>
To:     Thomas Falcon <tlfalcon@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        dnbanerg@...ibm.com, brking@...ux.vnet.ibm.com, pradeep@...ibm.com,
        sukadev@...ux.vnet.ibm.com, ljp@...ux.vnet.ibm.com,
        cforno12@...ux.ibm.com, ricklind@...ux.ibm.com
Subject: Re: [PATCH net-next 01/12] ibmvnic: Ensure that subCRQ entry reads
 are ordered

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@...ux.ibm.com>

Acked-by: Dany Madden <drt@...ux.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",