linux-kernel - Re: LTP test related to virtio releasing and reassigning resource leads to guest hung

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Date:   Thu, 10 Aug 2023 11:24:47 -0400
From:   Stefan Hajnoczi <stefanha@...il.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>
Cc:     "longguang.yue" <kvmluck@....com>,
        Michael Tokarev <mjt@....msk.ru>,
        "mst@...hat.com" <mst@...hat.com>,
        qemu-devel <qemu-devel@...gnu.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: LTP test related to virtio releasing and reassigning resource
 leads to guest hung

On Thu, 10 Aug 2023 at 10:14, Stefan Hajnoczi <stefanha@...hat.com> wrote:
>
> On Thu, Aug 10, 2023 at 06:35:32PM +0800, longguang.yue wrote:
> > could you please give me some tips to diagnose?  I could do tests on qemu 8.0, but product environment could not update.
> > I test on different kernel version 5.10.0-X, one is better and results show problem is more about host kernel  rather than qemu.
> >
> >
> > test cases are different combination of i440fx/q35 and virtio/scsi and kernel.
>
> Can you post the guest kernel messages (dmesg)? If the guest is hanging
> then it may be easiest to configure a serial console so the kernel
> messages are sent to the host where you can see them.
>
> Does the hang occur during the LTP code you linked or afterwards when
> the PCI device is bound to a virtio driver?

I didn't see your original email so I missed the panic. I'd still like
to see the earlier kernel messages before the panic in order to
understand how the PCI device is bound.

Is the vda device with hung I/O the same device that was accessed by
the LTP test earlier? I guess the LTP test runs against the device and
then the virtio driver binds to the device again afterwards?

>
> Which virtio device causes the problem?
>
> Can you describe the hang in more detail: is the guest still responsive
> (e.g. console or network)? Is the QEMU HMP/QMP monitor still responsive?
>
> Thanks,
> Stefan
>
> >
> >
> >
> >
> > thanks
> >
> >
> >
> >
> > ---- Replied Message ----
> > | From | Michael Tokarev<mjt@....msk.ru> |
> > | Date | 08/10/2023 17:08 |
> > | To | longguang.yue<kvmluck@....com> ,
> > qemu-devel<qemu-devel@...gnu.org> ,
> > linux-kernel<linux-kernel@...r.kernel.org> |
> > | Subject | Re: LTP test related to virtio releasing and reassigning resource leads to guest hung |
> > 10.08.2023 11:57, longguang.yue wrote:
> > Hi, all:
> > A ltp test leads to guest hung(io hung), the test releases virtio device resource and then reassign.
> > I find device’s mem prefetchable resource 64-bit is changed.
> >
> > ltp
> > test: https://github.com/linux-test-project/ltp/blob/522d7fba4afc84e07b252aa4cd91b241e81d6613/testcases/kernel/device-drivers/pci/tpci_kernel/ltp_tpci.c#L428
> >
> > Do you know what cause the problem?
> >
> > Thanks very much.
> >
> > --------------------------
> > ENV: kernel 5.10.0, qemu 6.2
> >
> > Current qemu is 8.1 (well, almost, to be released this month;
> > previous release is 8.0 anyway).
> >
> > This might be interesting to test in a current version before
> > going any further.
> >
> > Thanks,
> >
> > /mjt