[PATCH] net/netvsc: fix mtu_set in netvsc devices

[PATCH] net/netvsc: fix mtu_set in netvsc devices

[Alexander Skorichenko]

Prevent segfault in hn_reinit() caused by changing the MTU for
an incompletely initialized device.

Signed-off-by: Alexander Skorichenko <askorichenko@netgate.com>
---
 drivers/net/netvsc/hn_ethdev.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/netvsc/hn_ethdev.c b/drivers/net/netvsc/hn_ethdev.c
index b8a32832d7..f8cb05a118 100644
--- a/drivers/net/netvsc/hn_ethdev.c
+++ b/drivers/net/netvsc/hn_ethdev.c
@@ -1127,8 +1127,10 @@ hn_reinit(struct rte_eth_dev *dev, uint16_t mtu)
 	int i, ret = 0;
 
 	/* Point primary queues at new primary channel */
-	rxqs[0]->chan = hv->channels[0];
-	txqs[0]->chan = hv->channels[0];
+	if (rxqs[0]) {
+		rxqs[0]->chan = hv->channels[0];
+		txqs[0]->chan = hv->channels[0];
+	}
 
 	ret = hn_attach(hv, mtu);
 	if (ret)
@@ -1140,10 +1142,12 @@ hn_reinit(struct rte_eth_dev *dev, uint16_t mtu)
 		return ret;
 
 	/* Point any additional queues at new subchannels */
-	for (i = 1; i < dev->data->nb_rx_queues; i++)
-		rxqs[i]->chan = hv->channels[i];
-	for (i = 1; i < dev->data->nb_tx_queues; i++)
-		txqs[i]->chan = hv->channels[i];
+	if (rxqs[0]) {
+		for (i = 1; i < dev->data->nb_rx_queues; i++)
+			rxqs[i]->chan = hv->channels[i];
+		for (i = 1; i < dev->data->nb_tx_queues; i++)
+			txqs[i]->chan = hv->channels[i];
+	}
 
 	return ret;
 }
-- 
2.34.1

Re: [PATCH] net/netvsc: fix mtu_set in netvsc devices

[Stephen Hemminger]

On Fri, 28 Jun 2024 18:35:03 +0200
Alexander Skorichenko <askorichenko@netgate.com> wrote:

> Prevent segfault in hn_reinit() caused by changing the MTU for
> an incompletely initialized device.
> 
> Signed-off-by: Alexander Skorichenko <askorichenko@netgate.com>

How do you get in that state?
Maybe the init code should set up these pointers and avoid the problem.

Re: [PATCH] net/netvsc: fix mtu_set in netvsc devices

[Alexander Skorichenko]

[-- Attachment #1: Type: text/plain, Size: 2003 bytes --]

Hello,
The failure happens when running under VPP. In terms of dpdk calls the
following sequence of events occurs for a NetVSC device:

Durung device probing stage of VPP
   1. eth_hn_dev_init() memory for a single primary rx_queue is allocated
            dev->data->rx_queues[0] = 0, allocated, but not set yet
            no allocation happened for tx_queues[i] and non-primary
rx_queues[i]

During device setup stage of VPP from VPP's own generic dpdk_device_setup():
   2.  rte_eth_dev_set_mtu()
            currently it segfaults in hn_reinit() when trying to reach into
            dev->data->rx_queues[i], dev->data->tx_queues[i]
   3.  rte_eth_tx_queue_setup()
            dev->data->tx_queues[i] are being allocated and set
   4.  rte_eth_rx_queue_setup()
            dev->data->rx_queues[i] get allocated (i > 0) and set

So rx_queues[0] could be set in step 1, but rx_queues[i] and tx_queues[i]
are still NULL.
Allocating all the remaining rx/tx queues in step 1 would prevent the
crash, but then in steps 3-4 would go through releasing and allocating all
of the queues again.

Another comment regarding the uniform condition introduced in hn_reinit()
in the patch:
        if (dev->data->rx_queues[0] != NULL) ...
Because of the difference between rx/tx queues described above, it's
probably safer to extend the condition to check both rx and tx separately
        if (dev->data->rx_queues[0] != NULL && dev->data->tx_queues[0] !=
NULL)

- Alexander Skorichenko


On Sun, Jun 30, 2024 at 5:40 PM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Fri, 28 Jun 2024 18:35:03 +0200
> Alexander Skorichenko <askorichenko@netgate.com> wrote:
>
> > Prevent segfault in hn_reinit() caused by changing the MTU for
> > an incompletely initialized device.
> >
> > Signed-off-by: Alexander Skorichenko <askorichenko@netgate.com>
>
> How do you get in that state?
> Maybe the init code should set up these pointers and avoid the problem.
>

[-- Attachment #2: Type: text/html, Size: 2656 bytes --]

RE: [PATCH] net/netvsc: fix mtu_set in netvsc devices

[Long Li]

[-- Attachment #1: Type: text/plain, Size: 2299 bytes --]

Thank you, Alexander.

The patch looks good to me. With this patch, do you see other problems with VPP?

I'd like to get a review from @Sam Andrew<mailto:samandrew@microsoft.com>.

Acked-by: Long Li <longli@microsoft.com>


From: Alexander Skorichenko <askorichenko@netgate.com>
Sent: Tuesday, July 2, 2024 1:49 AM
To: stephen@networkplumber.org
Cc: Sam Andrew <samandrew@microsoft.com>; ferruh.yigit@amd.com; andrew.rybchenko@oktetlabs.ru; Long Li <longli@microsoft.com>; Wei Hu <weh@microsoft.com>; dev@dpdk.org; Matthew Smith <mgsmith@netgate.com>
Subject: Re: [PATCH] net/netvsc: fix mtu_set in netvsc devices

You don't often get email from askorichenko@netgate.com<mailto:askorichenko@netgate.com>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification>
Hello,
The failure happens when running under VPP. In terms of dpdk calls the following sequence of events occurs for a NetVSC device:

Durung device probing stage of VPP
   1. eth_hn_dev_init() memory for a single primary rx_queue is allocated
            dev->data->rx_queues[0] = 0, allocated, but not set yet
            no allocation happened for tx_queues[i] and non-primary rx_queues[i]

During device setup stage of VPP from VPP's own generic dpdk_device_setup():
   2.  rte_eth_dev_set_mtu()
            currently it segfaults in hn_reinit() when trying to reach into
            dev->data->rx_queues[i], dev->data->tx_queues[i]
   3.  rte_eth_tx_queue_setup()
            dev->data->tx_queues[i] are being allocated and set
   4.  rte_eth_rx_queue_setup()
            dev->data->rx_queues[i] get allocated (i > 0) and set

So rx_queues[0] could be set in step 1, but rx_queues[i] and tx_queues[i] are still NULL.
Allocating all the remaining rx/tx queues in step 1 would prevent the crash, but then in steps 3-4 would go through releasing and allocating all of the queues again.

Another comment regarding the uniform condition introduced in hn_reinit() in the patch:
        if (dev->data->rx_queues[0] != NULL) ...
Because of the difference between rx/tx queues described above, it's probably safer to extend the condition to check both rx and tx separately
        if (dev->data->rx_queues[0] != NULL && dev->data->tx_queues[0] != NULL)

- Alexander Skorichenko


[-- Attachment #2: Type: text/html, Size: 7026 bytes --]

Re: [PATCH] net/netvsc: fix mtu_set in netvsc devices

[Alexander Skorichenko]

[-- Attachment #1: Type: text/plain, Size: 502 bytes --]

Thanks.

>> With this patch, do you see other problems with VPP?
No further problems were noticed and MTU can be set to custom values.

- Alexander Skorichenko

On Wed, Jul 3, 2024 at 2:35 AM Long Li <longli@microsoft.com> wrote:

> Thank you, Alexander.
>
>
>
> The patch looks good to me. With this patch, do you see other problems
> with VPP?
>
>
>
> I’d like to get a review from @Sam Andrew <samandrew@microsoft.com>.
>
>
>
> Acked-by: Long Li <longli@microsoft.com>
>

[-- Attachment #2: Type: text/html, Size: 1487 bytes --]