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From: Nikos Dragazis <ndragazis@outlook.com.gr>
To: "spdk@lists.01.org" <spdk@lists.01.org>
Cc: Vangelis Koukis <vkoukis@arrikto.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [SPDK] virtio-vhost-user with virtio-scsi: end-to-end setup
Date: Sat, 6 Oct 2018 18:55:25 +0000	[thread overview]
Message-ID: <AM6PR07MB3864836F2F1AD09963BAA05998E40@AM6PR07MB3864.eurprd07.prod.outlook.com> (raw)
In-Reply-To: <F6F2A6264E145F47A18AB6DF8E87425D7034C019@IRSMSX102.ger.corp.intel.com>

Hi Pawel,

Thank you for your quick reply. I appreciate your help.

I’m sorry for the late response. I am glad to tell you that I have a
working demo at last. I have managed to solve my problem.

You were right about the IO channels. Function
spdk_scsi_dev_allocate_io_channels() fails to allocate the IO channel
for the virtio-scsi bdev target and function spdk_vhost_scsi_start()
fails to verify its return value. My actual segfault was due to a race
on the unique virtio-scsi bdev request queue between the creation and
the destruction of the IO channel in the vhost device backend. This led
to the IO channel pointer lun->io_channel being NULL after the
vhost-user negotiation, and the bdev layer segfaulted when accessing it
in response to an IO request.

After discovering this, and spending quite some time debugging it, I
searched the bug tracker and the commit history in case I had missed
something. It seems this was a recently discovered bug, which has
fortunately already been solved:

https://github.com/spdk/spdk/commit/9ddf6438310cc97b346d805a5969af7507e84fde#diff-d361b53e911663e8c6c5890fb046a79b

I had overlooked pulling from the official repo for a while, so I missed
the patch. It works just fine after pulling the newest changes.

So, I’ll make sure to work on the latest commits next time :)

Thanks again,
Nikos


On 21/09/2018 10:31 πμ, Wodkowski, PawelX wrote:
> Hi Nikos,
>
> About SPKD backtrace you got. There is something wrong with IO channel allocation.
> SPKD vhost-scsi  should check the result of spdk_scsi_dev_allocate_io_channels() in
> spdk_vhost_scsi_dev_add_tgt(). But this result is not checked :(
> You can add some check or assert there.
>
> Paweł


WARNING: multiple messages have this Message-ID (diff)
From: Nikos Dragazis <ndragazis at outlook.com.gr>
To: spdk@lists.01.org
Subject: Re: [SPDK] virtio-vhost-user with virtio-scsi: end-to-end setup
Date: Sat, 06 Oct 2018 18:55:25 +0000	[thread overview]
Message-ID: <AM6PR07MB3864836F2F1AD09963BAA05998E40@AM6PR07MB3864.eurprd07.prod.outlook.com> (raw)
In-Reply-To: F6F2A6264E145F47A18AB6DF8E87425D7034C019@IRSMSX102.ger.corp.intel.com

[-- Attachment #1: Type: text/plain, Size: 1742 bytes --]

Hi Pawel,

Thank you for your quick reply. I appreciate your help.

I’m sorry for the late response. I am glad to tell you that I have a
working demo at last. I have managed to solve my problem.

You were right about the IO channels. Function
spdk_scsi_dev_allocate_io_channels() fails to allocate the IO channel
for the virtio-scsi bdev target and function spdk_vhost_scsi_start()
fails to verify its return value. My actual segfault was due to a race
on the unique virtio-scsi bdev request queue between the creation and
the destruction of the IO channel in the vhost device backend. This led
to the IO channel pointer lun->io_channel being NULL after the
vhost-user negotiation, and the bdev layer segfaulted when accessing it
in response to an IO request.

After discovering this, and spending quite some time debugging it, I
searched the bug tracker and the commit history in case I had missed
something. It seems this was a recently discovered bug, which has
fortunately already been solved:

https://github.com/spdk/spdk/commit/9ddf6438310cc97b346d805a5969af7507e84fde#diff-d361b53e911663e8c6c5890fb046a79b

I had overlooked pulling from the official repo for a while, so I missed
the patch. It works just fine after pulling the newest changes.

So, I’ll make sure to work on the latest commits next time :)

Thanks again,
Nikos


On 21/09/2018 10:31 πμ, Wodkowski, PawelX wrote:
> Hi Nikos,
>
> About SPKD backtrace you got. There is something wrong with IO channel allocation.
> SPKD vhost-scsi  should check the result of spdk_scsi_dev_allocate_io_channels() in
> spdk_vhost_scsi_dev_add_tgt(). But this result is not checked :(
> You can add some check or assert there.
>
> Paweł


  reply	other threads:[~2018-10-06 18:55 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-20 22:06 [SPDK] virtio-vhost-user with virtio-scsi: end-to-end setup Nikos Dragazis
2018-09-21  7:31 ` Wodkowski, PawelX
2018-10-06 18:55   ` Nikos Dragazis [this message]
2018-10-06 18:55     ` Nikos Dragazis

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