Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Wed, Mar 02, 2011 at 12:34:24PM +0100, Jan Kiszka wrote:
> On 2011-03-02 11:56, Alon Levy wrote:
> > On Wed, Mar 02, 2011 at 09:22:35AM +0100, Jan Kiszka wrote:
> >> On 2011-03-01 13:58, Alon Levy wrote:
> >>> On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
>  On 2011-02-27 20:03, Alon Levy wrote:
> > On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
> >> On 2011-02-26 12:43, xming wrote:
> >>> When trying to start X (and it loads qxl driver) the kvm process just 
> >>> crashes.
> >
> > This is fixed by Gerd's attached patch (taken from rhel repository, 
> > don't know
> > why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> > well (separate email).
> 
>  Patch looks OK on first glance, but the changelog is misleading: This
>  was broken for _both_ trees, but upstream didn't detect the bug.
> >>>
> >>> So I didn't test with qemu not having this patch, but according to the 
> >>> discussion in the
> >>> launchpad bug the problem only happens with qemu-kvm. This doesn't rule 
> >>> out it being a
> >>> bug, perhaps it is just triggered much less frequently I guess.
> >>
> >> Again: qemu-kvm has the instrumentation to detect the bug, qemu is
> >> lacking this, but both trees will break subtly if cpu_current_env is not
> >> properly restored.
> > 
> > ok, so what do you want to be done further before this patch is applied?
> 
> The patch posted to qemu-devel just requires a changelog that correctly
> reflects what it addresses (and where).

Just sent,

Alon

> 
> Jan
> 


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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Jan Kiszka]

On 2011-03-02 11:56, Alon Levy wrote:
> On Wed, Mar 02, 2011 at 09:22:35AM +0100, Jan Kiszka wrote:
>> On 2011-03-01 13:58, Alon Levy wrote:
>>> On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
 On 2011-02-27 20:03, Alon Levy wrote:
> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
>> On 2011-02-26 12:43, xming wrote:
>>> When trying to start X (and it loads qxl driver) the kvm process just 
>>> crashes.
>
> This is fixed by Gerd's attached patch (taken from rhel repository, don't 
> know
> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> well (separate email).

 Patch looks OK on first glance, but the changelog is misleading: This
 was broken for _both_ trees, but upstream didn't detect the bug.
>>>
>>> So I didn't test with qemu not having this patch, but according to the 
>>> discussion in the
>>> launchpad bug the problem only happens with qemu-kvm. This doesn't rule out 
>>> it being a
>>> bug, perhaps it is just triggered much less frequently I guess.
>>
>> Again: qemu-kvm has the instrumentation to detect the bug, qemu is
>> lacking this, but both trees will break subtly if cpu_current_env is not
>> properly restored.
> 
> ok, so what do you want to be done further before this patch is applied?

The patch posted to qemu-devel just requires a changelog that correctly
reflects what it addresses (and where).

Jan



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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Wed, Mar 02, 2011 at 09:22:35AM +0100, Jan Kiszka wrote:
> On 2011-03-01 13:58, Alon Levy wrote:
> > On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
> >> On 2011-02-27 20:03, Alon Levy wrote:
> >>> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
>  On 2011-02-26 12:43, xming wrote:
> > When trying to start X (and it loads qxl driver) the kvm process just 
> > crashes.
> >>>
> >>> This is fixed by Gerd's attached patch (taken from rhel repository, don't 
> >>> know
> >>> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> >>> well (separate email).
> >>
> >> Patch looks OK on first glance, but the changelog is misleading: This
> >> was broken for _both_ trees, but upstream didn't detect the bug.
> > 
> > So I didn't test with qemu not having this patch, but according to the 
> > discussion in the
> > launchpad bug the problem only happens with qemu-kvm. This doesn't rule out 
> > it being a
> > bug, perhaps it is just triggered much less frequently I guess.
> 
> Again: qemu-kvm has the instrumentation to detect the bug, qemu is
> lacking this, but both trees will break subtly if cpu_current_env is not
> properly restored.

ok, so what do you want to be done further before this patch is applied?

> 
> Jan
> 


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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Jan Kiszka]

On 2011-03-01 13:58, Alon Levy wrote:
> On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
>> On 2011-02-27 20:03, Alon Levy wrote:
>>> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
 On 2011-02-26 12:43, xming wrote:
> When trying to start X (and it loads qxl driver) the kvm process just 
> crashes.
>>>
>>> This is fixed by Gerd's attached patch (taken from rhel repository, don't 
>>> know
>>> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
>>> well (separate email).
>>
>> Patch looks OK on first glance, but the changelog is misleading: This
>> was broken for _both_ trees, but upstream didn't detect the bug.
> 
> So I didn't test with qemu not having this patch, but according to the 
> discussion in the
> launchpad bug the problem only happens with qemu-kvm. This doesn't rule out 
> it being a
> bug, perhaps it is just triggered much less frequently I guess.

Again: qemu-kvm has the instrumentation to detect the bug, qemu is
lacking this, but both trees will break subtly if cpu_current_env is not
properly restored.

Jan



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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
> On 2011-02-27 20:03, Alon Levy wrote:
> > On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
> >> On 2011-02-26 12:43, xming wrote:
> >>> When trying to start X (and it loads qxl driver) the kvm process just 
> >>> crashes.
> > 
> > This is fixed by Gerd's attached patch (taken from rhel repository, don't 
> > know
> > why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> > well (separate email).
> 
> Patch looks OK on first glance, but the changelog is misleading: This
> was broken for _both_ trees, but upstream didn't detect the bug.

So I didn't test with qemu not having this patch, but according to the 
discussion in the
launchpad bug the problem only happens with qemu-kvm. This doesn't rule out it 
being a
bug, perhaps it is just triggered much less frequently I guess.

> 
> My concerns regarding other side effects of juggling with global mutex
> in spice code remain.
> 
> Jan
> 


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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Rick Vernam]

On Sunday 27 February 2011 13:03:14 Alon Levy wrote:
> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
> > On 2011-02-26 12:43, xming wrote:
> > > When trying to start X (and it loads qxl driver) the kvm process just
> > > crashes.
> 
> This is fixed by Gerd's attached patch (taken from rhel repository, don't
> know why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list
> as well (separate email).
> 

This patch also fixed
https://bugs.launchpad.net/bugs/723871
I created the bug report on launchpad, but I suppose it should be left open 
until the patch hits qemu-kvm?

-Rick
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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[xming]

On Sun, Feb 27, 2011 at 8:03 PM, Alon Levy  wrote:
> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
>> On 2011-02-26 12:43, xming wrote:
>> > When trying to start X (and it loads qxl driver) the kvm process just 
>> > crashes.
>
> This is fixed by Gerd's attached patch (taken from rhel repository, don't know
> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as well 
> (separate email).

I can confirm that this patch fixes the issue, thanks a lot

cheers
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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Sun, Feb 27, 2011 at 08:27:01PM +0100, Jan Kiszka wrote:
> On 2011-02-27 20:16, Alon Levy wrote:
> > On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
> >> On 2011-02-27 20:03, Alon Levy wrote:
> >>> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
>  On 2011-02-26 12:43, xming wrote:
> > When trying to start X (and it loads qxl driver) the kvm process just 
> > crashes.
> >>>
> >>> This is fixed by Gerd's attached patch (taken from rhel repository, don't 
> >>> know
> >>> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> >>> well (separate email).
> >>
> >> Patch looks OK on first glance, but the changelog is misleading: This
> >> was broken for _both_ trees, but upstream didn't detect the bug.
> >>
> > 
> > The trees the patch commit message refers to are qemu and qemu-kvm.
> 
> The same did I.
> 
> > qemu doesn't even have cpu_single_env.
> 
> Really? Check again. :)
> 
> > It didn't talk about two qemu-kvm trees.
> > 
> >> My concerns regarding other side effects of juggling with global mutex
> >> in spice code remain.
> > 
> > I know there used to be a mutex in spice code and during the upstreaming 
> > process it
> > got ditched in favor of the qemu global io mutex. I would have rather 
> > deferred this
> > to Gerd since he wrote this, but he is not available atm.
> 
> It's not necessarily bad to drop the io mutex, but it is more tricky
> than it may appear on first glance.

The problem with not dropping it is that we may be in vga mode and create
updates synthtically (i.e. qemu created and not driver created) that access the
framebuffer and need to be locked so the framebuffer isn't updated at the same
time. We drop the mutex only when we are about to call the dispatcher, which 
basically
waits on red_worker (a libspice-server thread) to do some work. red_worker may
in turn callback into qxl in qemu, which may try to acquire the lock. (the
many may's here are just reflections of the codepaths).

> 
> Jan
> 


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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Sun, Feb 27, 2011 at 08:27:01PM +0100, Jan Kiszka wrote:
> On 2011-02-27 20:16, Alon Levy wrote:
> > On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
> >> On 2011-02-27 20:03, Alon Levy wrote:
> >>> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
>  On 2011-02-26 12:43, xming wrote:
> > When trying to start X (and it loads qxl driver) the kvm process just 
> > crashes.
> >>>
> >>> This is fixed by Gerd's attached patch (taken from rhel repository, don't 
> >>> know
> >>> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> >>> well (separate email).
> >>
> >> Patch looks OK on first glance, but the changelog is misleading: This
> >> was broken for _both_ trees, but upstream didn't detect the bug.
> >>
> > 
> > The trees the patch commit message refers to are qemu and qemu-kvm.
> 
> The same did I.
> 
> > qemu doesn't even have cpu_single_env.
> 
> Really? Check again. :)

Sorry, grepped the wrong repo. I'll send this to qemu-devel too then.

> 
> > It didn't talk about two qemu-kvm trees.
> > 
> >> My concerns regarding other side effects of juggling with global mutex
> >> in spice code remain.
> > 
> > I know there used to be a mutex in spice code and during the upstreaming 
> > process it
> > got ditched in favor of the qemu global io mutex. I would have rather 
> > deferred this
> > to Gerd since he wrote this, but he is not available atm.
> 
> It's not necessarily bad to drop the io mutex, but it is more tricky
> than it may appear on first glance.
> 
> Jan
> 


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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Jan Kiszka]

On 2011-02-27 20:16, Alon Levy wrote:
> On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
>> On 2011-02-27 20:03, Alon Levy wrote:
>>> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
 On 2011-02-26 12:43, xming wrote:
> When trying to start X (and it loads qxl driver) the kvm process just 
> crashes.
>>>
>>> This is fixed by Gerd's attached patch (taken from rhel repository, don't 
>>> know
>>> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
>>> well (separate email).
>>
>> Patch looks OK on first glance, but the changelog is misleading: This
>> was broken for _both_ trees, but upstream didn't detect the bug.
>>
> 
> The trees the patch commit message refers to are qemu and qemu-kvm.

The same did I.

> qemu doesn't even have cpu_single_env.

Really? Check again. :)

> It didn't talk about two qemu-kvm trees.
> 
>> My concerns regarding other side effects of juggling with global mutex
>> in spice code remain.
> 
> I know there used to be a mutex in spice code and during the upstreaming 
> process it
> got ditched in favor of the qemu global io mutex. I would have rather 
> deferred this
> to Gerd since he wrote this, but he is not available atm.

It's not necessarily bad to drop the io mutex, but it is more tricky
than it may appear on first glance.

Jan



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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Sun, Feb 27, 2011 at 08:11:26PM +0100, Jan Kiszka wrote:
> On 2011-02-27 20:03, Alon Levy wrote:
> > On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
> >> On 2011-02-26 12:43, xming wrote:
> >>> When trying to start X (and it loads qxl driver) the kvm process just 
> >>> crashes.
> > 
> > This is fixed by Gerd's attached patch (taken from rhel repository, don't 
> > know
> > why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as 
> > well (separate email).
> 
> Patch looks OK on first glance, but the changelog is misleading: This
> was broken for _both_ trees, but upstream didn't detect the bug.
> 

The trees the patch commit message refers to are qemu and qemu-kvm. qemu 
doesn't even
have cpu_single_env. It didn't talk about two qemu-kvm trees.

> My concerns regarding other side effects of juggling with global mutex
> in spice code remain.

I know there used to be a mutex in spice code and during the upstreaming 
process it
got ditched in favor of the qemu global io mutex. I would have rather deferred 
this
to Gerd since he wrote this, but he is not available atm.

> 
> Jan
> 


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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Jan Kiszka]

On 2011-02-27 20:03, Alon Levy wrote:
> On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
>> On 2011-02-26 12:43, xming wrote:
>>> When trying to start X (and it loads qxl driver) the kvm process just 
>>> crashes.
> 
> This is fixed by Gerd's attached patch (taken from rhel repository, don't know
> why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as well 
> (separate email).

Patch looks OK on first glance, but the changelog is misleading: This
was broken for _both_ trees, but upstream didn't detect the bug.

My concerns regarding other side effects of juggling with global mutex
in spice code remain.

Jan



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Re: [Qemu-devel] Re: kvm crashes with spice while loading qxl

[Alon Levy]

On Sat, Feb 26, 2011 at 01:29:01PM +0100, Jan Kiszka wrote:
> On 2011-02-26 12:43, xming wrote:
> > When trying to start X (and it loads qxl driver) the kvm process just 
> > crashes.

This is fixed by Gerd's attached patch (taken from rhel repository, don't know
why it wasn't pushed to qemu-kvm upstream). I'll send it to kvm list as well 
(separate email).

> > 
> > qemu-kvm 0.14
> > 
> > startup line
> > 
> > /usr/bin/kvm -name spaceball,process=spaceball -m 1024 -kernel
> > /boot/bzImage-2.6.37.2-guest -append "root=/dev/vda ro" -smp 1 -netdev
> > type=tap,id=spaceball0,script=kvm-ifup-brloc,vhost=on -device
> > virtio-net-pci,netdev=spaceball0,mac=00:16:3e:00:08:01 -drive
> > file=/dev/volume01/G-spaceball,if=virtio -vga qxl -spice
> > port=5957,disable-ticketing -monitor
> > telnet:192.168.0.254:10007,server,nowait,nodelay -pidfile
> > /var/run/kvm/spaceball.pid
> > 
> > host is running vanilla 2.6.37.1 on amd64.
> > 
> > Here is the bt
> > 
> > # gdb /usr/bin/qemu-system-x86_64
> > GNU gdb (Gentoo 7.2 p1) 7.2
> > Copyright (C) 2010 Free Software Foundation, Inc.
> > License GPLv3+: GNU GPL version 3 or later 
> > 
> > This is free software: you are free to change and redistribute it.
> > There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> > and "show warranty" for details.
> > This GDB was configured as "x86_64-pc-linux-gnu".
> > For bug reporting instructions, please see:
> > ...
> > Reading symbols from /usr/bin/qemu-system-x86_64...done.
> > (gdb) set args -name spaceball,process=spaceball -m 1024 -kernel
> > /boot/bzImage-2.6.37.2-guest -append "root=/dev/vda ro" -smp 1 -netdev
> > type=tap,id=spaceball0,script=kvm-ifup-brloc,vhost=on -device
> > virtio-net-pci,netdev=spaceball0,mac=00:16:3e:00:08:01 -drive
> > file=/dev/volume01/G-spaceball,if=virtio -vga qxl -spice
> > port=5957,disable-ticketing -monitor
> > telnet:192.168.0.254:10007,server,nowait,nodelay -pidfile
> > /var/run/kvm/spaceball.pid
> > (gdb) run
> > Starting program: /usr/bin/qemu-system-x86_64 -name
> > spaceball,process=spaceball -m 1024 -kernel
> > /boot/bzImage-2.6.37.2-guest -append "root=/dev/vda ro" -smp 1 -netdev
> > type=tap,id=spaceball0,script=kvm-ifup-brloc,vhost=on -device
> > virtio-net-pci,netdev=spaceball0,mac=00:16:3e:00:08:01 -drive
> > file=/dev/volume01/G-spaceball,if=virtio -vga qxl -spice
> > port=5957,disable-ticketing -monitor
> > telnet:192.168.0.254:10007,server,nowait,nodelay -pidfile
> > /var/run/kvm/spaceball.pid
> > [Thread debugging using libthread_db enabled]
> > do_spice_init: starting 0.6.0
> > spice_server_add_interface: SPICE_INTERFACE_KEYBOARD
> > spice_server_add_interface: SPICE_INTERFACE_MOUSE
> > [New Thread 0x74802710 (LWP 30294)]
> > spice_server_add_interface: SPICE_INTERFACE_QXL
> > [New Thread 0x7fffaacae710 (LWP 30295)]
> > red_worker_main: begin
> > handle_dev_destroy_surfaces:
> > handle_dev_destroy_surfaces:
> > handle_dev_input: start
> > [New Thread 0x7fffaa4ad710 (LWP 30298)]
> > [New Thread 0x7fffa9cac710 (LWP 30299)]
> > [New Thread 0x7fffa94ab710 (LWP 30300)]
> > [New Thread 0x7fffa8caa710 (LWP 30301)]
> > [New Thread 0x7fffa3fff710 (LWP 30302)]
> > [New Thread 0x7fffa37fe710 (LWP 30303)]
> > [New Thread 0x7fffa2ffd710 (LWP 30304)]
> > [New Thread 0x7fffa27fc710 (LWP 30305)]
> > [New Thread 0x7fffa1ffb710 (LWP 30306)]
> > [New Thread 0x7fffa17fa710 (LWP 30307)]
> > reds_handle_main_link:
> > reds_show_new_channel: channel 1:0, connected successfully, over Non Secure 
> > link
> > reds_main_handle_message: net test: latency 5.636000 ms, bitrate
> > 11027768 bps (10.516899 Mbps)
> > reds_show_new_channel: channel 2:0, connected successfully, over Non Secure 
> > link
> > red_dispatcher_set_peer:
> > handle_dev_input: connect
> > handle_new_display_channel: jpeg disabled
> > handle_new_display_channel: zlib-over-glz disabled
> > reds_show_new_channel: channel 4:0, connected successfully, over Non Secure 
> > link
> > red_dispatcher_set_cursor_peer:
> > handle_dev_input: cursor connect
> > reds_show_new_channel: channel 3:0, connected successfully, over Non Secure 
> > link
> > inputs_link:
> > [New Thread 0x7fffa07f8710 (LWP 30312)]
> > [New Thread 0x7fff9fff7710 (LWP 30313)]
> > [New Thread 0x7fff9f7f6710 (LWP 30314)]
> > [New Thread 0x7fff9eff5710 (LWP 30315)]
> > [New Thread 0x7fff9e7f4710 (LWP 30316)]
> > [New Thread 0x7fff9dff3710 (LWP 30317)]
> > [New Thread 0x7fff9d7f2710 (LWP 30318)]
> > qemu-system-x86_64:
> > /var/tmp/portage/app-emulation/qemu-kvm-0.14.0/work/qemu-kvm-0.14.0/qemu-kvm.c:1724:
> > kvm_mutex_unlock: Assertion `!cpu_single_env' failed.
> > 
> > Program received signal SIGABRT, Aborted.
> > [Switching to Thread 0x74802710 (LWP 30294)]
> > 0x75daa165 in raise () from /lib/libc.so.6
> > (gdb)
> > (gdb)
> > (gdb)
> > (gdb)
> > (gdb) bt
> > #0  0x75daa165 in raise () from /lib/libc.so.6
> > #1  0x75dab580 in abort () from /lib/libc.so.6
> > #2