[fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Ian Pilcher]

Is this a known problem?  I just tried using nested vmx for the first
time since upgrading my system from F19 (3.12.?? at the time) to F20,
and I cannot start any L2 guests.  The L2 guest appears to hang almost
immediately after starting, consuming 100% of one of the L1 guest's
VCPUs.

If I reboot with kernel-3.12.10-300.fc20.x86_64, the problem does not
occur.

Any known workaround?  (Other than using 3.12.10?)

Thanks!

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Ian Pilcher                                         arequipeno@gmail.com
           Sent from the cloud -- where it's already tomorrow
========================================================================

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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Paolo Bonzini]

Il 04/03/2014 03:40, Ian Pilcher ha scritto:
> Is this a known problem?  I just tried using nested vmx for the first
> time since upgrading my system from F19 (3.12.?? at the time) to F20,
> and I cannot start any L2 guests.  The L2 guest appears to hang almost
> immediately after starting, consuming 100% of one of the L1 guest's
> VCPUs.
>
> If I reboot with kernel-3.12.10-300.fc20.x86_64, the problem does not
> occur.
>
> Any known workaround?  (Other than using 3.12.10?)

There is a fix on the way to the 3.13 kernel.

You can open a Fedora bug and ask them to include 
http://article.gmane.org/gmane.linux.kernel.stable/82043/raw in the kernel.

Paolo
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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Kashyap Chamarthy]

On Tue, Mar 04, 2014 at 09:13:40AM +0100, Paolo Bonzini wrote:
> Il 04/03/2014 03:40, Ian Pilcher ha scritto:
> >Is this a known problem?  I just tried using nested vmx for the first
> >time since upgrading my system from F19 (3.12.?? at the time) to F20,
> >and I cannot start any L2 guests.  The L2 guest appears to hang almost
> >immediately after starting, consuming 100% of one of the L1 guest's
> >VCPUs.
> >
> >If I reboot with kernel-3.12.10-300.fc20.x86_64, the problem does not
> >occur.
> >
> >Any known workaround?  (Other than using 3.12.10?)

If you want to try, I made a Fedora Kernel scratch build (i.e. not
official) with fix Paolo pointed to below and this works for me:

  http://koji.fedoraproject.org/koji/taskinfo?taskID=6577700

(NOTE: Fedora Scratch build URLs won't last more than 10 days or so)

> 
> There is a fix on the way to the 3.13 kernel.
> 
> You can open a Fedora bug and ask them to include
> http://article.gmane.org/gmane.linux.kernel.stable/82043/raw in the
> kernel.
> 
> Paolo
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
/kashyap

Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Kashyap Chamarthy]

On Tue, Mar 04, 2014 at 03:00:22PM +0530, Kashyap Chamarthy wrote:
> On Tue, Mar 04, 2014 at 09:13:40AM +0100, Paolo Bonzini wrote:
> > Il 04/03/2014 03:40, Ian Pilcher ha scritto:
> > >Is this a known problem?  I just tried using nested vmx for the first
> > >time since upgrading my system from F19 (3.12.?? at the time) to F20,
> > >and I cannot start any L2 guests.  The L2 guest appears to hang almost
> > >immediately after starting, consuming 100% of one of the L1 guest's
> > >VCPUs.
> > >
> > >If I reboot with kernel-3.12.10-300.fc20.x86_64, the problem does not
> > >occur.

Err, I missed to read this. Sorry about that.

> > >
> > >Any known workaround?  (Other than using 3.12.10?)
> 
> If you want to try, I made a Fedora Kernel scratch build (i.e. not
> official) with fix Paolo pointed to below and this works for me:
> 
>   http://koji.fedoraproject.org/koji/taskinfo?taskID=6577700
> 
> (NOTE: Fedora Scratch build URLs won't last more than 10 days or so)
> 
> > 
> > There is a fix on the way to the 3.13 kernel.
> > 
> > You can open a Fedora bug and ask them to include
> > http://article.gmane.org/gmane.linux.kernel.stable/82043/raw in the
> > kernel.
> > 
> > Paolo
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> -- 
> /kashyap

-- 
/kashyap

Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Ian Pilcher]

On 03/04/2014 03:30 AM, Kashyap Chamarthy wrote:
> If you want to try, I made a Fedora Kernel scratch build (i.e. not
> official) with fix Paolo pointed to below and this works for me:
> 
>   http://koji.fedoraproject.org/koji/taskinfo?taskID=6577700

Works here.  Thanks!

-- 
========================================================================
Ian Pilcher                                         arequipeno@gmail.com
           Sent from the cloud -- where it's already tomorrow
========================================================================

Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Richard W.M. Jones]

On Tue, Mar 04, 2014 at 09:13:40AM +0100, Paolo Bonzini wrote:
> Il 04/03/2014 03:40, Ian Pilcher ha scritto:
> >Is this a known problem?  I just tried using nested vmx for the first
> >time since upgrading my system from F19 (3.12.?? at the time) to F20,
> >and I cannot start any L2 guests.  The L2 guest appears to hang almost
> >immediately after starting, consuming 100% of one of the L1 guest's
> >VCPUs.
> >
> >If I reboot with kernel-3.12.10-300.fc20.x86_64, the problem does not
> >occur.
> >
> >Any known workaround?  (Other than using 3.12.10?)
> 
> There is a fix on the way to the 3.13 kernel.
> 
> You can open a Fedora bug and ask them to include
> http://article.gmane.org/gmane.linux.kernel.stable/82043/raw in the
> kernel.

Thanks for fixing this.  It affects a lot of libguestfs users too.

I opened this bug:

https://bugzilla.redhat.com/show_bug.cgi?id=1073663

Rich.

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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Vasiliy Tolstov]

2014-03-07 1:59 GMT+04:00 Richard W.M. Jones <rjones@redhat.com>:
> On Tue, Mar 04, 2014 at 09:13:40AM +0100, Paolo Bonzini wrote:
>> Il 04/03/2014 03:40, Ian Pilcher ha scritto:
>> >Is this a known problem?  I just tried using nested vmx for the first
>> >time since upgrading my system from F19 (3.12.?? at the time) to F20,
>> >and I cannot start any L2 guests.  The L2 guest appears to hang almost
>> >immediately after starting, consuming 100% of one of the L1 guest's
>> >VCPUs.
>> >
>> >If I reboot with kernel-3.12.10-300.fc20.x86_64, the problem does not
>> >occur.
>> >
>> >Any known workaround?  (Other than using 3.12.10?)
>>
>> There is a fix on the way to the 3.13 kernel.
>>
>> You can open a Fedora bug and ask them to include
>> http://article.gmane.org/gmane.linux.kernel.stable/82043/raw in the
>> kernel.
>
> Thanks for fixing this.  It affects a lot of libguestfs users too.
>
> I opened this bug:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1073663
>
> Rich.


If i use 3.13.6 kernel that have alredy this patch, but sometimes i
get kernel panic, what can i do?
P.S. I'm using nested virt, fault from L2

[   10.942007] PANIC: double fault, error_code: 0x0
[   10.942007] CPU: 0 PID: 182 Comm: systemd-journal Not tainted 3.13.6 #3
[   10.942007] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   10.942007] task: ffff88001cc08000 ti: ffff88001d70e000 task.ti:
ffff88001d70e000
[   10.942007] RIP: 0033:[<00007fe61b2fce8a>]  [<00007fe61b2fce8a>]
0x7fe61b2fce8a
[   10.942007] RSP: 002b:00007fffee7468d8  EFLAGS: 00010286
[   10.942007] RAX: 0000000000000000 RBX: 000000000043344e RCX: 0000000000430a70
[   10.942007] RDX: 0000000000000010 RSI: 00000000ffffffff RDI: 0000000000430a70
[   10.942007] RBP: 00007fffee747130 R08: 0000000000000003 R09: 00007fe61be81780
[   10.942007] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
[   10.942007] R13: 0000000001c9c380 R14: 0000000000000003 R15: 00007fffee747148
[   10.942007] FS:  00007fe61be81780(0000) GS:ffff88001f800000(0000)
knlGS:0000000000000000
[   10.942007] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   10.942007] CR2: 0000000000000000 CR3: 000000001e1a2000 CR4: 00000000000006f0
[   10.942007]
[   10.942007] Kernel panic - not syncing: Machine halted.


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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Richard W.M. Jones]

On Fri, Mar 14, 2014 at 03:52:03PM +0400, Vasiliy Tolstov wrote:
> If i use 3.13.6 kernel that have alredy this patch, but sometimes i
> get kernel panic, what can i do?
> P.S. I'm using nested virt, fault from L2

It could be there is another, less frequent, bug in nested KVM.
I'm assuming this is on Intel hardware?

From the libguestfs point of view what you can do is to force TCG:

    export LIBGUESTFS_BACKEND_SETTINGS=force_tcg

Unfortunately this only has an effect in libguestfs >= 1.25.24.  We're
going to have the new version in Fedora 20 real soon -- probably
before the end of this month.  Or you can compile the Rawhide version
on F20.

Rich.

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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Vasiliy Tolstov]

2014-03-14 15:58 GMT+04:00 Richard W.M. Jones <rjones@redhat.com>:
> It could be there is another, less frequent, bug in nested KVM.
> I'm assuming this is on Intel hardware?
>
> From the libguestfs point of view what you can do is to force TCG:
>
>     export LIBGUESTFS_BACKEND_SETTINGS=force_tcg
>
> Unfortunately this only has an effect in libguestfs >= 1.25.24.  We're
> going to have the new version in Fedora 20 real soon -- probably
> before the end of this month.  Or you can compile the Rawhide version
> on F20.


Thanks for answer. I'm not using libguestfs. I'm try tun vm inside vm
via libvirt.
is that possible to debug this issue ? How can i help?
P.S. Yes i'm using intel hardware.

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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Richard W.M. Jones]

On Fri, Mar 14, 2014 at 04:11:13PM +0400, Vasiliy Tolstov wrote:
> 2014-03-14 15:58 GMT+04:00 Richard W.M. Jones <rjones@redhat.com>:
> > It could be there is another, less frequent, bug in nested KVM.
> > I'm assuming this is on Intel hardware?
> >
> > From the libguestfs point of view what you can do is to force TCG:
> >
> >     export LIBGUESTFS_BACKEND_SETTINGS=force_tcg
> >
> > Unfortunately this only has an effect in libguestfs >= 1.25.24.  We're
> > going to have the new version in Fedora 20 real soon -- probably
> > before the end of this month.  Or you can compile the Rawhide version
> > on F20.
> 
> 
> Thanks for answer. I'm not using libguestfs. I'm try tun vm inside vm
> via libvirt.

You can set the VM <domain type="qemu">.  Of course it'll run quite
slowly.

> is that possible to debug this issue ? How can i help?

Complete logs from the guest.
Any messages from qemu or the host.
& put all of that into a full bug report.

Rich.

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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Vasiliy Tolstov]

2014-03-14 16:16 GMT+04:00 Richard W.M. Jones <rjones@redhat.com>:
> You can set the VM <domain type="qemu">.  Of course it'll run quite
> slowly.
>
>> is that possible to debug this issue ? How can i help?
>
> Complete logs from the guest.
> Any messages from qemu or the host.
> & put all of that into a full bug report.


Where i can find submission form for bug report? (I'm using exherbo
linux, but it does not have like debian or sles personal patches and
using only upstream)

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Re: [fedora-virt] 3.13 - Nested KVM (vmx) totally broken?

[Richard W.M. Jones]

On Fri, Mar 14, 2014 at 04:39:48PM +0400, Vasiliy Tolstov wrote:
> 2014-03-14 16:16 GMT+04:00 Richard W.M. Jones <rjones@redhat.com>:
> > You can set the VM <domain type="qemu">.  Of course it'll run quite
> > slowly.
> >
> >> is that possible to debug this issue ? How can i help?
> >
> > Complete logs from the guest.
> > Any messages from qemu or the host.
> > & put all of that into a full bug report.
> 
> 
> Where i can find submission form for bug report? (I'm using exherbo
> linux, but it does not have like debian or sles personal patches and
> using only upstream)

I suspect this is going to be a kernel bug, in which case:

https://bugzilla.kernel.org/

For libvirt bugs it would be:

https://bugzilla.redhat.com/enter_bug.cgi?component=libvirt&product=Virtualization+Tools

Rich.

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