Re: [PATCH net 1/2] ibmvnic: Ensure that SCRQ entry reads are correctly ordered
Thomas Falcon writes:
> On 11/24/20 11:43 PM, Michael Ellerman wrote:
>> Thomas Falcon writes:
>>> Ensure that received Subordinate Command-Response Queue (SCRQ)
>>> entries are properly read in order by the driver. These queues
>>> are used in the ibmvnic device to process RX buffer and TX completion
>>> descriptors. dma_rmb barriers have been added after checking for a
>>> pending descriptor to ensure the correct descriptor entry is checked
>>> and after reading the SCRQ descriptor to ensure the entire
>>> descriptor is read before processing.
>>>
>>> Fixes: 032c5e828 ("Driver for IBM System i/p VNIC protocol")
>>> Signed-off-by: Thomas Falcon
>>> ---
>>> drivers/net/ethernet/ibm/ibmvnic.c | 8
>>> 1 file changed, 8 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
>>> b/drivers/net/ethernet/ibm/ibmvnic.c
>>> index 2aa40b2..489ed5e 100644
>>> --- a/drivers/net/ethernet/ibm/ibmvnic.c
>>> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
>>> @@ -2403,6 +2403,8 @@ 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();
>> I'd be happier if these comments were more specific about which read(s)
>> they are ordering vs which other read(s).
>>
>> I'm sure it's obvious to you, but it may not be to a future author,
>> and/or after the code has been refactored over time.
>
> Thank you for reviewing! I will submit a v2 soon with clearer comments
> on the reads being ordered here.
Thanks.
cheers
Re: [PATCH net 1/2] ibmvnic: Ensure that SCRQ entry reads are correctly ordered
On 11/24/20 11:43 PM, Michael Ellerman wrote:
Thomas Falcon writes:
Ensure that received Subordinate Command-Response Queue (SCRQ)
entries are properly read in order by the driver. These queues
are used in the ibmvnic device to process RX buffer and TX completion
descriptors. dma_rmb barriers have been added after checking for a
pending descriptor to ensure the correct descriptor entry is checked
and after reading the SCRQ descriptor to ensure the entire
descriptor is read before processing.
Fixes: 032c5e828 ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Thomas Falcon
---
drivers/net/ethernet/ibm/ibmvnic.c | 8
1 file changed, 8 insertions(+)
diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
b/drivers/net/ethernet/ibm/ibmvnic.c
index 2aa40b2..489ed5e 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2403,6 +2403,8 @@ 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();
I'd be happier if these comments were more specific about which read(s)
they are ordering vs which other read(s).
I'm sure it's obvious to you, but it may not be to a future author,
and/or after the code has been refactored over time.
Thank you for reviewing! I will submit a v2 soon with clearer comments
on the reads being ordered here.
Thanks,
Tom
next = ibmvnic_next_scrq(adapter, adapter->rx_scrq[scrq_num]);
rx_buff =
(struct ibmvnic_rx_buff *)be64_to_cpu(next->
@@ -3098,6 +3100,9 @@ static int ibmvnic_complete_tx(struct ibmvnic_adapter
*adapter,
unsigned int pool = scrq->pool_index;
int num_entries = 0;
+ /* ensure that the correct descriptor entry is read */
+ dma_rmb();
+
next = ibmvnic_next_scrq(adapter, scrq);
for (i = 0; i < next->tx_comp.num_comps; i++) {
if (next->tx_comp.rcs[i]) {
@@ -3498,6 +3503,9 @@ static union sub_crq *ibmvnic_next_scrq(struct
ibmvnic_adapter *adapter,
}
spin_unlock_irqrestore(>lock, flags);
+ /* ensure that the entire SCRQ descriptor is read */
+ dma_rmb();
+
return entry;
}
cheers
Re: [PATCH net 1/2] ibmvnic: Ensure that SCRQ entry reads are correctly ordered
Thomas Falcon writes:
> Ensure that received Subordinate Command-Response Queue (SCRQ)
> entries are properly read in order by the driver. These queues
> are used in the ibmvnic device to process RX buffer and TX completion
> descriptors. dma_rmb barriers have been added after checking for a
> pending descriptor to ensure the correct descriptor entry is checked
> and after reading the SCRQ descriptor to ensure the entire
> descriptor is read before processing.
>
> Fixes: 032c5e828 ("Driver for IBM System i/p VNIC protocol")
> Signed-off-by: Thomas Falcon
> ---
> drivers/net/ethernet/ibm/ibmvnic.c | 8
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
> b/drivers/net/ethernet/ibm/ibmvnic.c
> index 2aa40b2..489ed5e 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -2403,6 +2403,8 @@ 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();
I'd be happier if these comments were more specific about which read(s)
they are ordering vs which other read(s).
I'm sure it's obvious to you, but it may not be to a future author,
and/or after the code has been refactored over time.
> next = ibmvnic_next_scrq(adapter, adapter->rx_scrq[scrq_num]);
> rx_buff =
> (struct ibmvnic_rx_buff *)be64_to_cpu(next->
> @@ -3098,6 +3100,9 @@ static int ibmvnic_complete_tx(struct ibmvnic_adapter
> *adapter,
> unsigned int pool = scrq->pool_index;
> int num_entries = 0;
>
> + /* ensure that the correct descriptor entry is read */
> + dma_rmb();
> +
> next = ibmvnic_next_scrq(adapter, scrq);
> for (i = 0; i < next->tx_comp.num_comps; i++) {
> if (next->tx_comp.rcs[i]) {
> @@ -3498,6 +3503,9 @@ static union sub_crq *ibmvnic_next_scrq(struct
> ibmvnic_adapter *adapter,
> }
> spin_unlock_irqrestore(>lock, flags);
>
> + /* ensure that the entire SCRQ descriptor is read */
> + dma_rmb();
> +
> return entry;
> }
cheers
[PATCH net 1/2] ibmvnic: Ensure that SCRQ entry reads are correctly ordered
Ensure that received Subordinate Command-Response Queue (SCRQ)
entries are properly read in order by the driver. These queues
are used in the ibmvnic device to process RX buffer and TX completion
descriptors. dma_rmb barriers have been added after checking for a
pending descriptor to ensure the correct descriptor entry is checked
and after reading the SCRQ descriptor to ensure the entire
descriptor is read before processing.
Fixes: 032c5e828 ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Thomas Falcon
---
drivers/net/ethernet/ibm/ibmvnic.c | 8
1 file changed, 8 insertions(+)
diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
b/drivers/net/ethernet/ibm/ibmvnic.c
index 2aa40b2..489ed5e 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2403,6 +2403,8 @@ 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->
@@ -3098,6 +3100,9 @@ static int ibmvnic_complete_tx(struct ibmvnic_adapter
*adapter,
unsigned int pool = scrq->pool_index;
int num_entries = 0;
+ /* ensure that the correct descriptor entry is read */
+ dma_rmb();
+
next = ibmvnic_next_scrq(adapter, scrq);
for (i = 0; i < next->tx_comp.num_comps; i++) {
if (next->tx_comp.rcs[i]) {
@@ -3498,6 +3503,9 @@ static union sub_crq *ibmvnic_next_scrq(struct
ibmvnic_adapter *adapter,
}
spin_unlock_irqrestore(>lock, flags);
+ /* ensure that the entire SCRQ descriptor is read */
+ dma_rmb();
+
return entry;
}
--
1.8.3.1
