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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Matan Azrad <matan@mellanox.com>, Xiao Wang <xiao.w.wang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v1 3/4] vhost: improve device ready definition
Date: Mon, 22 Jun 2020 14:32:57 +0200
Message-ID: <62311463-2bc1-7f8b-1ec0-da31418e1d75@redhat.com> (raw)
In-Reply-To: <AM0PR0502MB4019A51B6C6B2A87A57876ECD2970@AM0PR0502MB4019.eurprd05.prod.outlook.com>



On 6/22/20 12:06 PM, Matan Azrad wrote:
> 
> Hi Maxime
> 
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Monday, June 22, 2020 11:56 AM
>> To: Matan Azrad <matan@mellanox.com>; Xiao Wang
>> <xiao.w.wang@intel.com>
>> Cc: dev@dpdk.org
>> Subject: Re: [PATCH v1 3/4] vhost: improve device ready definition
>>
>>
>>
>> On 6/22/20 10:41 AM, Matan Azrad wrote:
>>>> The issue is if you only check ready state only before and after the
>>>> message affecting the ring is handled, it can be ready at both
>>>> stages, while the rings have changed and state change callback should
>> have been called.
>>> But in this version I checked twice, before message handler and after
>> message handler, so it should catch any update.
>>
>> No, this is not enough, we have to check also during some handlers, so that
>> the ready state is invalidated because sometimes it will be ready before and
>> after the message handler but with different values.
>>
>> That's what I did in my example patch:
>> @@ -1847,15 +1892,16 @@ vhost_user_set_vring_kick(struct virtio_net
>> **pdev, struct VhostUserMsg *msg,
>>
>> ...
>>
>>         if (vq->kickfd >= 0)
>>                 close(vq->kickfd);
>> +
>> +       vq->kickfd = VIRTIO_UNINITIALIZED_EVENTFD;
>> +
>> +       vhost_user_update_vring_state(dev, file.index);
>> +
>>         vq->kickfd = file.fd;
>>
>>
>> Without that, the ready check will return ready before and after the kickfd
>> changed and the driver won't be notified.
> 
> The driver will be notified in the next VHOST_USER_SET_VRING_ENABLE message according to v1.
> 
> One of our assumption we agreed on in the design mail is that it doesn't make sense that QEMU will change queue configuration without enabling the queue again.
> Because of that we decided to force calling state callback again when QEMU send VHOST_USER_SET_VRING_ENABLE(1) message even if the queue is already ready.
> So when driver/app see state enable->enable, it should take into account that the queue configuration was probably changed.
> 
> I think that this assumption is correct according to the QEMU code.

Yes, this was our initial assumption.
But now looking into the details of the implementation, I find it is
even cleaner & clearer not to do this assumption.

> That's why I prefer to collect all the ready checks callbacks (queue state and device new\conf) to one function that will be called after the message handler:
> Pseudo:
>  vhost_user_update_ready_statuses() {
> 	switch (msg):
> 		case enable:
> 			if(enable is 1)
> 				force queue state =1.
> 		case callfd
> 		case kickfd
> 				.....
> 		Check queue and device ready + call callbacks if needed..
> 		Default
> 			Return;
> }

I find it more natural to "invalidate" ready state where it is handled
(after vring_invalidate(), before setting new FD for call & kick, ...)



  reply	other threads:[~2020-06-22 12:33 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-18 16:28 [dpdk-dev] [PATCH v1 0/4] vhost: improve ready state Matan Azrad
2020-06-18 16:28 ` [dpdk-dev] [PATCH v1 1/4] vhost: support host notifier queue configuration Matan Azrad
2020-06-19  6:44   ` Maxime Coquelin
2020-06-19 13:28     ` Matan Azrad
2020-06-19 14:01       ` Maxime Coquelin
2020-06-21  6:26         ` Matan Azrad
2020-06-22  8:06           ` Maxime Coquelin
2020-06-18 16:28 ` [dpdk-dev] [PATCH v1 2/4] vhost: skip access lock when vDPA is configured Matan Azrad
2020-06-19  6:49   ` Maxime Coquelin
2020-06-18 16:28 ` [dpdk-dev] [PATCH v1 3/4] vhost: improve device ready definition Matan Azrad
2020-06-19  7:41   ` Maxime Coquelin
2020-06-19 12:04     ` Maxime Coquelin
2020-06-19 13:11     ` Matan Azrad
2020-06-19 13:54       ` Maxime Coquelin
2020-06-21  6:20         ` Matan Azrad
2020-06-22  8:04           ` Maxime Coquelin
2020-06-22  8:41             ` Matan Azrad
2020-06-22  8:56               ` Maxime Coquelin
2020-06-22 10:06                 ` Matan Azrad
2020-06-22 12:32                   ` Maxime Coquelin [this message]
2020-06-22 13:43                     ` Matan Azrad
2020-06-22 14:55                       ` Maxime Coquelin
2020-06-22 15:51                         ` Matan Azrad
2020-06-22 16:47                           ` Maxime Coquelin
2020-06-23  9:02                             ` Matan Azrad
2020-06-23  9:19                               ` Maxime Coquelin
2020-06-23 11:53                                 ` Matan Azrad
2020-06-23 13:55                                   ` Maxime Coquelin
2020-06-23 14:33                                     ` Maxime Coquelin
2020-06-23 14:52                                     ` Matan Azrad
2020-06-23 15:18                                       ` Maxime Coquelin
2020-06-24  5:54                                         ` Matan Azrad
2020-06-24  7:22                                           ` Maxime Coquelin
2020-06-24  8:38                                             ` Matan Azrad
2020-06-24  9:12                                               ` Maxime Coquelin
2020-06-18 16:28 ` [dpdk-dev] [PATCH v1 4/4] vdpa/mlx5: support queue update Matan Azrad
2020-06-25 13:38 ` [dpdk-dev] [PATCH v2 0/5] vhost: improve ready state Matan Azrad
2020-06-25 13:38   ` [dpdk-dev] [PATCH v2 1/5] vhost: skip access lock when vDPA is configured Matan Azrad
2020-06-28  3:06     ` Xia, Chenbo
2020-06-25 13:38   ` [dpdk-dev] [PATCH v2 2/5] vhost: improve device readiness notifications Matan Azrad
2020-06-26 12:10     ` Maxime Coquelin
2020-06-28  3:08     ` Xia, Chenbo
2020-06-25 13:38   ` [dpdk-dev] [PATCH v2 3/5] vhost: handle memory hotplug with vDPA devices Matan Azrad
2020-06-26 12:15     ` Maxime Coquelin
2020-06-28  3:18     ` Xia, Chenbo
2020-06-25 13:38   ` [dpdk-dev] [PATCH v2 4/5] vhost: notify virtq file descriptor update Matan Azrad
2020-06-26 12:19     ` Maxime Coquelin
2020-06-28  3:19     ` Xia, Chenbo
2020-06-25 13:38   ` [dpdk-dev] [PATCH v2 5/5] vdpa/mlx5: support queue update Matan Azrad
2020-06-26 12:29     ` Maxime Coquelin
2020-06-29 14:08   ` [dpdk-dev] [PATCH v3 0/6] vhost: improve ready state Matan Azrad
2020-06-29 14:08     ` [dpdk-dev] [PATCH v3 1/6] vhost: support host notifier queue configuration Matan Azrad
2020-06-29 14:08     ` [dpdk-dev] [PATCH v3 2/6] vhost: skip access lock when vDPA is configured Matan Azrad
2020-06-29 14:08     ` [dpdk-dev] [PATCH v3 3/6] vhost: improve device readiness notifications Matan Azrad
2020-06-29 14:08     ` [dpdk-dev] [PATCH v3 4/6] vhost: handle memory hotplug with vDPA devices Matan Azrad
2020-06-29 14:08     ` [dpdk-dev] [PATCH v3 5/6] vhost: notify virtq file descriptor update Matan Azrad
2020-06-29 14:08     ` [dpdk-dev] [PATCH v3 6/6] vdpa/mlx5: support queue update Matan Azrad
2020-06-29 17:24     ` [dpdk-dev] [PATCH v3 0/6] vhost: improve ready state Maxime Coquelin
2020-07-17  1:41       ` Wang, Yinan

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