* [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered
@ 2021-01-25 23:20 Lijun Pan
2021-01-28 1:01 ` Jakub Kicinski
0 siblings, 1 reply; 5+ messages in thread
From: Lijun Pan @ 2021-01-25 23:20 UTC (permalink / raw)
To: netdev; +Cc: Lijun Pan
Ensure that received Command-Response Queue (CRQ) entries are
properly read in order by the driver. dma_rmb barrier has
been added before accessing the CRQ descriptor to ensure
the entire descriptor is read before processing.
Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
---
v2: drop dma_wmb according to Jakub's opinion
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 9778c83150f1..d84369bd5fc9 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -5084,6 +5084,14 @@ static void ibmvnic_tasklet(struct tasklet_struct *t)
while (!done) {
/* Pull all the valid messages off the CRQ */
while ((crq = ibmvnic_next_crq(adapter)) != NULL) {
+ /* Ensure that the entire CRQ descriptor queue->msgs
+ * has been loaded before reading its contents.
+ * This barrier makes sure ibmvnic_next_crq()'s
+ * crq->generic.first & IBMVNIC_CRQ_CMD_RSP is loaded
+ * before ibmvnic_handle_crq()'s
+ * switch(gen_crq->first) and switch(gen_crq->cmd).
+ */
+ dma_rmb();
ibmvnic_handle_crq(crq, adapter);
crq->generic.first = 0;
}
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered
2021-01-25 23:20 [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered Lijun Pan
@ 2021-01-28 1:01 ` Jakub Kicinski
2021-01-28 1:22 ` Lijun Pan
0 siblings, 1 reply; 5+ messages in thread
From: Jakub Kicinski @ 2021-01-28 1:01 UTC (permalink / raw)
To: Lijun Pan; +Cc: netdev
On Mon, 25 Jan 2021 17:20:23 -0600 Lijun Pan wrote:
> Ensure that received Command-Response Queue (CRQ) entries are
> properly read in order by the driver. dma_rmb barrier has
> been added before accessing the CRQ descriptor to ensure
> the entire descriptor is read before processing.
>
> Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
> Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
> ---
> v2: drop dma_wmb according to Jakub's opinion
>
> 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 9778c83150f1..d84369bd5fc9 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -5084,6 +5084,14 @@ static void ibmvnic_tasklet(struct tasklet_struct *t)
> while (!done) {
> /* Pull all the valid messages off the CRQ */
> while ((crq = ibmvnic_next_crq(adapter)) != NULL) {
> + /* Ensure that the entire CRQ descriptor queue->msgs
> + * has been loaded before reading its contents.
I still find this sentence confusing, maybe you mean to say stored
instead of loaded?
> + * This barrier makes sure ibmvnic_next_crq()'s
> + * crq->generic.first & IBMVNIC_CRQ_CMD_RSP is loaded
> + * before ibmvnic_handle_crq()'s
> + * switch(gen_crq->first) and switch(gen_crq->cmd).
Yup, that makes perfect sense. It's about ordering of the loads.
> + */
> + dma_rmb();
> ibmvnic_handle_crq(crq, adapter);
> crq->generic.first = 0;
> }
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered
2021-01-28 1:01 ` Jakub Kicinski
@ 2021-01-28 1:22 ` Lijun Pan
2021-01-28 1:31 ` Jakub Kicinski
0 siblings, 1 reply; 5+ messages in thread
From: Lijun Pan @ 2021-01-28 1:22 UTC (permalink / raw)
To: Jakub Kicinski; +Cc: Lijun Pan, netdev
On Wed, Jan 27, 2021 at 7:06 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Mon, 25 Jan 2021 17:20:23 -0600 Lijun Pan wrote:
> > Ensure that received Command-Response Queue (CRQ) entries are
> > properly read in order by the driver. dma_rmb barrier has
> > been added before accessing the CRQ descriptor to ensure
> > the entire descriptor is read before processing.
> >
> > Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
> > Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
> > ---
> > v2: drop dma_wmb according to Jakub's opinion
> >
> > 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 9778c83150f1..d84369bd5fc9 100644
> > --- a/drivers/net/ethernet/ibm/ibmvnic.c
> > +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> > @@ -5084,6 +5084,14 @@ static void ibmvnic_tasklet(struct tasklet_struct *t)
> > while (!done) {
> > /* Pull all the valid messages off the CRQ */
> > while ((crq = ibmvnic_next_crq(adapter)) != NULL) {
> > + /* Ensure that the entire CRQ descriptor queue->msgs
> > + * has been loaded before reading its contents.
>
> I still find this sentence confusing, maybe you mean to say stored
> instead of loaded?
The above 2 lines are the general description. The below 4 lines are
detailed explanations. If it is still confusing, we can delete the above
2 lines of comments.
>
> > + * This barrier makes sure ibmvnic_next_crq()'s
> > + * crq->generic.first & IBMVNIC_CRQ_CMD_RSP is loaded
> > + * before ibmvnic_handle_crq()'s
> > + * switch(gen_crq->first) and switch(gen_crq->cmd).
>
> Yup, that makes perfect sense. It's about ordering of the loads.
>
> > + */
> > + dma_rmb();
> > ibmvnic_handle_crq(crq, adapter);
> > crq->generic.first = 0;
> > }
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered
2021-01-28 1:22 ` Lijun Pan
@ 2021-01-28 1:31 ` Jakub Kicinski
2021-01-28 1:39 ` Lijun Pan
0 siblings, 1 reply; 5+ messages in thread
From: Jakub Kicinski @ 2021-01-28 1:31 UTC (permalink / raw)
To: Lijun Pan; +Cc: Lijun Pan, netdev
On Wed, 27 Jan 2021 19:22:25 -0600 Lijun Pan wrote:
> On Wed, Jan 27, 2021 at 7:06 PM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > On Mon, 25 Jan 2021 17:20:23 -0600 Lijun Pan wrote:
> > > Ensure that received Command-Response Queue (CRQ) entries are
> > > properly read in order by the driver. dma_rmb barrier has
> > > been added before accessing the CRQ descriptor to ensure
> > > the entire descriptor is read before processing.
> > >
> > > Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
> > > Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
> > > ---
> > > v2: drop dma_wmb according to Jakub's opinion
> > >
> > > 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 9778c83150f1..d84369bd5fc9 100644
> > > --- a/drivers/net/ethernet/ibm/ibmvnic.c
> > > +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> > > @@ -5084,6 +5084,14 @@ static void ibmvnic_tasklet(struct tasklet_struct *t)
> > > while (!done) {
> > > /* Pull all the valid messages off the CRQ */
> > > while ((crq = ibmvnic_next_crq(adapter)) != NULL) {
> > > + /* Ensure that the entire CRQ descriptor queue->msgs
> > > + * has been loaded before reading its contents.
> >
> > I still find this sentence confusing, maybe you mean to say stored
> > instead of loaded?
>
> The above 2 lines are the general description. The below 4 lines are
> detailed explanations. If it is still confusing, we can delete the above
> 2 lines of comments.
Yes, I'd find the comment clearer without them, thanks.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered
2021-01-28 1:31 ` Jakub Kicinski
@ 2021-01-28 1:39 ` Lijun Pan
0 siblings, 0 replies; 5+ messages in thread
From: Lijun Pan @ 2021-01-28 1:39 UTC (permalink / raw)
To: Jakub Kicinski; +Cc: Lijun Pan, netdev
On Wed, Jan 27, 2021 at 7:31 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Wed, 27 Jan 2021 19:22:25 -0600 Lijun Pan wrote:
> > On Wed, Jan 27, 2021 at 7:06 PM Jakub Kicinski <kuba@kernel.org> wrote:
> > >
> > > On Mon, 25 Jan 2021 17:20:23 -0600 Lijun Pan wrote:
> > > > Ensure that received Command-Response Queue (CRQ) entries are
> > > > properly read in order by the driver. dma_rmb barrier has
> > > > been added before accessing the CRQ descriptor to ensure
> > > > the entire descriptor is read before processing.
> > > >
> > > > Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
> > > > Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
> > > > ---
> > > > v2: drop dma_wmb according to Jakub's opinion
> > > >
> > > > 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 9778c83150f1..d84369bd5fc9 100644
> > > > --- a/drivers/net/ethernet/ibm/ibmvnic.c
> > > > +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> > > > @@ -5084,6 +5084,14 @@ static void ibmvnic_tasklet(struct tasklet_struct *t)
> > > > while (!done) {
> > > > /* Pull all the valid messages off the CRQ */
> > > > while ((crq = ibmvnic_next_crq(adapter)) != NULL) {
> > > > + /* Ensure that the entire CRQ descriptor queue->msgs
> > > > + * has been loaded before reading its contents.
> > >
> > > I still find this sentence confusing, maybe you mean to say stored
> > > instead of loaded?
> >
> > The above 2 lines are the general description. The below 4 lines are
> > detailed explanations. If it is still confusing, we can delete the above
> > 2 lines of comments.
>
> Yes, I'd find the comment clearer without them, thanks.
v3 has been sent out:
https://patchwork.kernel.org/project/netdevbpf/patch/20210128013442.88319-1-ljp@linux.ibm.com/
Thanks,
Lijun
^ permalink raw reply [flat|nested] 5+ messages in thread
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2021-01-25 23:20 [PATCH net v2] ibmvnic: Ensure that CRQ entry read are correctly ordered Lijun Pan
2021-01-28 1:01 ` Jakub Kicinski
2021-01-28 1:22 ` Lijun Pan
2021-01-28 1:31 ` Jakub Kicinski
2021-01-28 1:39 ` Lijun Pan
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