Re: [dpdk-dev] [Suspected-Phishing][PATCH] net/vhost: fix redundant queue state event

[Maxime Coquelin]

On 6/26/19 8:37 AM, Noa Ezra wrote:

Hi,

-----Original Message-----
From: Maxime Coquelin [mailto:maxime.coque...@redhat.com]
Sent: Tuesday, June 25, 2019 11:24 AM
To: Noa Ezra <n...@mellanox.com>
Cc: Matan Azrad <ma...@mellanox.com>; dev@dpdk.org; sta...@dpdk.org
Subject: Re: [Suspected-Phishing][PATCH] net/vhost: fix redundant queue
state event



On 6/25/19 9:04 AM, Noa Ezra wrote:

Hi,
What do you think about this patch?

Thanks,
Noa.

-----Original Message-----
From: Noa Ezra [mailto:n...@mellanox.com]
Sent: Wednesday, June 19, 2019 9:16 AM
To: maxime.coque...@redhat.com
Cc: Matan Azrad <ma...@mellanox.com>; dev@dpdk.org; Noa Ezra
<n...@mellanox.com>; sta...@dpdk.org
Subject: [Suspected-Phishing][PATCH] net/vhost: fix redundant queue
state event

In some situations, when a virtual machine is starting,
vring_state_changed can be called while there was no change in the
queue state. This fix makes sure that there was really a change in
the queue state before calling the callback for EVENT_QUEUE_STATE.

Fixes: ee584e9710b9 ("vhost: add driver on top of the library")
Cc: sta...@dpdk.org
Reviewed-by: Matan Azrad <ma...@mellanox.com>
---
   drivers/net/vhost/rte_eth_vhost.c | 4 ++++
   1 file changed, 4 insertions(+)

diff --git a/drivers/net/vhost/rte_eth_vhost.c
b/drivers/net/vhost/rte_eth_vhost.c
index cad1e5c..fbe7a37 100644
--- a/drivers/net/vhost/rte_eth_vhost.c
+++ b/drivers/net/vhost/rte_eth_vhost.c
@@ -855,6 +855,10 @@ struct vhost_xstats_name_off {
        /* won't be NULL */
        state = vring_states[eth_dev->data->port_id];
        rte_spinlock_lock(&state->lock);
+       if (state->cur[vring] == enable) {
+               rte_spinlock_unlock(&state->lock);
+               return 0;
+       }

        state->cur[vring] = enable;
        state->max_vring = RTE_MAX(vring, state->max_vring);

Maybe the application would want to be notified a new queue is available,
even if it is disabled?

Can you please look again? As I understand it, "enable" is the "new state" 
parameter (can be enable/disable).
In this fix I make sure that there was really a change in the state before 
calling EVENT_QUEUE_STATE (with no change in the state).

Ok, I get it.

Maybe we would want to update state->max_vring even if we don't sent the
event?

Thanks,
Maxime

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1.8.3.1