Re: KVM and Prempt?

Re: KVM and Prempt?

[Back, Michael (ext)]

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2.6.31.1 should be 2.6.23.1 - sorry

> _____________________________________________ 
> Von: 	Back, Michael (ext)  
> Gesendet:	Friday, October 19, 2007 3:16 PM
> An:	'kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org'
> Betreff:	KVM and Prempt?
> 
> 
> Hallo,
> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a AMD Opteron and on a Intel Xeon, on both it works fine!
> 
> After this test I patch the kernel with the current prempt-patch and on both it doesn't works!
> -> After a very short time - I could see the windows startup screen - the complied system froze!
> 
> Has someone ever tried to do the same and it works?
> Or will KVM with Windows on a prempt kernel 
> - never work?
> - maybe work in the future?
> - should now work but this .. and this > ...>  should be done and consider?
> 
> With best regards,
> Michael Back
> 
> #########################
> ASTRUM IT GmbH 
> Michael Back
> 
> Dipl.-Ing. Univ. 
> software engineer
> Projectmanagement
> 
> Am Wolfsmantel 46
> 91058 Erlangen, Germany 
> Tel.: +49 (91 31) 94 08 - 374 
> Fax: +49 (91 31) 94 08 - 108 
> <mailto:HYPERLINK "mailto:Michael.Back-uO8URJBSKRghFhg+JK9F0w@public.gmane.org" Michael.Back-uO8URJBSKRghFhg+JK9F0w@public.gmane.org <mailto:HYPERLINK > > 
> 
> contact address by Siemens 
> Siemens AG
> Medical Solutions
> MED MRZ
> Allee am Roethelheimpark 2
> 91052 Erlangen, Germany
> Tel.: +49 (9131) 84-5307
> Fax: +49 (9131) 84-8767
> <mailto:HYPERLINK "mailto:Michael.Back.ext-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org" Michael.Back.ext-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org <mailto:HYPERLINK > >
> 
> Siemens Aktiengesellschaft: Chairman of the Supervisory Board: Gerhard Cromme; Managing Board: Peter Loescher, Chairman, President and Chief Executive Officer; 
> Heinrich Hiesinger, Joe Kaeser, Rudi Lamprecht, Eduardo Montes, Juergen Radomski, Erich R. Reinhardt, Hermann Requardt, Uriel J. Sharef, Peter Y. Solmssen, Klaus Wucherer;
>  Registered offices: Berlin and Munich; Commercial registries: Berlin Charlottenburg, HRB 12300, Munich, HRB 6684; WEEE-Reg.-No. DE 23691322
> 

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Re: KVM and Prempt?

[Gregory Haskins]

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Hi Michael,

On Fri, 2007-10-19 at 15:32 +0200, Back, Michael (ext) wrote:
> 
> 
> 2.6.31.1 should be 2.6.23.1 - sorry
> 
> _____________________________________________  
> Von:    Back, Michael (ext)   
> Gesendet:       Friday, October 19, 2007 3:16 PM 
> An:     'kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org' 
> Betreff:        KVM and Prempt?
> 
> 
> Hallo, 
> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a AMD Opteron
> and on a Intel Xeon, on both it works fine!
> 
> After this test I patch the kernel with the current prempt-patch and
> on both it doesn't works! 

Are you referring to the -rt patch?

> -> After a very short time - I could see the windows startup screen -
> the complied system froze!
> 
> Has someone ever tried to do the same and it works? 
> Or will KVM with Windows on a prempt kernel  
> - never work? 
> - maybe work in the future? 
> - should now work but this .. and this … should be done and consider?
> 
> With best regards, 
> Michael Back
> 
> ######################### 
> ASTRUM IT GmbH
> Michael Back
> 
> Dipl.-Ing. Univ.
> software engineer
> Projectmanagement
> 
> Am Wolfsmantel 46
> 91058 Erlangen, Germany
> Tel.: +49 (91 31) 94 08 - 374
> Fax: +49 (91 31) 94 08 - 108  
> <mailto:HYPERLINK "mailto:Michael.Back-uO8URJBSKRghFhg+JK9F0w@public.gmane.org"
> Michael.Back-uO8URJBSKRghFhg+JK9F0w@public.gmane.org>  
> 
> contact address by Siemens
> Siemens AG
> Medical Solutions
> MED MRZ
> Allee am Roethelheimpark 2
> 91052 Erlangen, Germany
> Tel.: +49 (9131) 84-5307
> Fax: +49 (9131) 84-8767
> <mailto:HYPERLINK "mailto:Michael.Back.ext-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org"
> Michael.Back.ext-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>
> 
> Siemens Aktiengesellschaft: Chairman of the Supervisory Board: Gerhard
> Cromme; Managing Board: Peter Loescher, Chairman, President and Chief
> Executive Officer; 
> 
> Heinrich Hiesinger, Joe Kaeser, Rudi Lamprecht, Eduardo Montes,
> Juergen Radomski, Erich R. Reinhardt, Hermann Requardt, Uriel J.
> Sharef, Peter Y. Solmssen, Klaus Wucherer;
> 
>  Registered offices: Berlin and Munich; Commercial registries: Berlin
> Charlottenburg, HRB 12300, Munich, HRB 6684; WEEE-Reg.-No. DE 23691322
> 
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> _______________________________________________ kvm-devel mailing list kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/kvm-devel

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Re: KVM and Prempt?

[Back, Michael (ext)]

 
Hi Gregory,

>Hi Michael,

>On Fri, 2007-10-19 at 15:32 +0200, Back, Michael (ext) wrote:
>> 
>> 
>> 2.6.31.1 should be 2.6.23.1 - sorry
>> 
>> _____________________________________________  
>> Von:    Back, Michael (ext)   
>> Gesendet:       Friday, October 19, 2007 3:16 PM 
>> An:     'kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org' 
>> Betreff:        KVM and Prempt?
>> 
>> 
>> Hallo, 
>> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a AMD Opteron
>> and on a Intel Xeon, on both it works fine!
>> 
>> After this test I patch the kernel with the current prempt-patch and
>> on both it doesn't works! 

>Are you referring to the -rt patch?

Yes, I take the patch from
http://www.kernel.org/pub/linux/kernel/projects/rt/

>> -> After a very short time - I could see the windows startup screen -
>> the complied system froze!
>> 
>> Has someone ever tried to do the same and it works? 
>> Or will KVM with Windows on a prempt kernel  
>> - never work? 
>> - maybe work in the future? 
>> - should now work but this .. and this ... should be done and
consider?
>> 
>> With best regards, 
>> Michael Back
>> 
>> ######################### 
>> ASTRUM IT GmbH
>> Michael Back
>> 
>> Dipl.-Ing. Univ.
>> software engineer
>> Projectmanagement
>> 
>> Am Wolfsmantel 46
>> 91058 Erlangen, Germany
>> Tel.: +49 (91 31) 94 08 - 374
>> Fax: +49 (91 31) 94 08 - 108  
>> <mailto:HYPERLINK "mailto:Michael.Back-uO8URJBSKRghFhg+JK9F0w@public.gmane.org"
>> Michael.Back-uO8URJBSKRghFhg+JK9F0w@public.gmane.org>  
>> 
>> contact address by Siemens
>> Siemens AG
>> Medical Solutions
>> MED MRZ
>> Allee am Roethelheimpark 2
>> 91052 Erlangen, Germany
>> Tel.: +49 (9131) 84-5307
>> Fax: +49 (9131) 84-8767
>> <mailto:HYPERLINK "mailto:Michael.Back.ext-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org"
>> Michael.Back.ext-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>
>> 
>> Siemens Aktiengesellschaft: Chairman of the Supervisory Board:
Gerhard
>> Cromme; Managing Board: Peter Loescher, Chairman, President and Chief
>> Executive Officer; 
>> 
>> Heinrich Hiesinger, Joe Kaeser, Rudi Lamprecht, Eduardo Montes,
>> Juergen Radomski, Erich R. Reinhardt, Hermann Requardt, Uriel J.
>> Sharef, Peter Y. Solmssen, Klaus Wucherer;
>> 
>>  Registered offices: Berlin and Munich; Commercial registries: Berlin
>> Charlottenburg, HRB 12300, Munich, HRB 6684; WEEE-Reg.-No. DE
23691322
>> 
>>
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Re: KVM and Prempt?

[Gregory Haskins]

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On Fri, 2007-10-19 at 16:17 +0200, Back, Michael (ext) wrote:

> >Are you referring to the -rt patch?
> 
> Yes, I take the patch from
> http://www.kernel.org/pub/linux/kernel/projects/rt/
> 

Ah, yes.  There were problems in the past with running KVM on -rt if you
have the full kit enabled.  Its possible they are still not fixed.

I had patches to address this issue for an older KVM and had it up and
running on a full PREEMPT_RT kernel, but they have become quite stale at
this point.  I will be picking up this work again sometime in the near
future, so watch this space.

Are you building KVM as a module from the -rt tree, or as an external
module?

-Greg

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_______________________________________________
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Re: KVM and Prempt?

[Back, Michael (ext)]

> -----Ursprüngliche Nachricht-----
> Von: Gregory Haskins [mailto:ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org] 
> Gesendet: Friday, October 19, 2007 5:27 PM
> An: Back, Michael (ext)
> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> Betreff: Re: AW: [kvm-devel] KVM and Prempt?
> 
> On Fri, 2007-10-19 at 16:17 +0200, Back, Michael (ext) wrote:
> 
> > >Are you referring to the -rt patch?
> > 
> > Yes, I take the patch from
> > http://www.kernel.org/pub/linux/kernel/projects/rt/
> > 
> 
> Ah, yes.  There were problems in the past with running KVM on 
> -rt if you
> have the full kit enabled.  Its possible they are still not fixed.
> 
> I had patches to address this issue for an older KVM and had it up and
> running on a full PREEMPT_RT kernel, but they have become 
> quite stale at
> this point.  I will be picking up this work again sometime in the near
> future, so watch this space.
> 
> Are you building KVM as a module from the -rt tree, or as an external
> module?

I use a external module, last try was kvm-46!

Michael

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Re: KVM and Prempt?

[Avi Kivity]

Back, Michael (ext) wrote:
>> -----Ursprüngliche Nachricht-----
>> Von: Gregory Haskins [mailto:ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org] 
>> Gesendet: Friday, October 19, 2007 5:27 PM
>> An: Back, Michael (ext)
>> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
>> Betreff: Re: AW: [kvm-devel] KVM and Prempt?
>>
>> On Fri, 2007-10-19 at 16:17 +0200, Back, Michael (ext) wrote:
>>
>>     
>>>> Are you referring to the -rt patch?
>>>>         
>>> Yes, I take the patch from
>>> http://www.kernel.org/pub/linux/kernel/projects/rt/
>>>
>>>       
>> Ah, yes.  There were problems in the past with running KVM on 
>> -rt if you
>> have the full kit enabled.  Its possible they are still not fixed.
>>
>> I had patches to address this issue for an older KVM and had it up and
>> running on a full PREEMPT_RT kernel, but they have become 
>> quite stale at
>> this point.  I will be picking up this work again sometime in the near
>> future, so watch this space.
>>
>> Are you building KVM as a module from the -rt tree, or as an external
>> module?
>>     
>
> I use a external module, last try was kvm-46!
>
>   

Make sure CONFIG_PREEMPT_NOTIFIER is selected in your .config.  You'll
have to adjust Kconfig or select the in-tree kvm for that.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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Re: KVM and Prempt?

[Back, Michael (ext)]

> -----Ursprüngliche Nachricht-----
> Von: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org 
> [mailto:kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org] Im Auftrag 
> von Avi Kivity
> Gesendet: Monday, October 22, 2007 9:40 AM
> An: Back, Michael (ext)
> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> Betreff: Re: [kvm-devel] KVM and Prempt?
> 
> Back, Michael (ext) wrote:
> >> -----Ursprüngliche Nachricht-----
> >> Von: Gregory Haskins [mailto:ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org] 
> >> Gesendet: Friday, October 19, 2007 5:27 PM
> >> An: Back, Michael (ext)
> >> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> >> Betreff: Re: AW: [kvm-devel] KVM and Prempt?
> >>
> >> On Fri, 2007-10-19 at 16:17 +0200, Back, Michael (ext) wrote:
> >>
> >>     
> >>>> Are you referring to the -rt patch?
> >>>>         
> >>> Yes, I take the patch from
> >>> http://www.kernel.org/pub/linux/kernel/projects/rt/
> >>>
> >>>       
> >> Ah, yes.  There were problems in the past with running KVM on 
> >> -rt if you
> >> have the full kit enabled.  Its possible they are still not fixed.
> >>
> >> I had patches to address this issue for an older KVM and 
> had it up and
> >> running on a full PREEMPT_RT kernel, but they have become 
> >> quite stale at
> >> this point.  I will be picking up this work again sometime 
> in the near
> >> future, so watch this space.
> >>
> >> Are you building KVM as a module from the -rt tree, or as 
> an external
> >> module?
> >>     
> >
> > I use a external module, last try was kvm-46!
> >
> >   
> 
> Make sure CONFIG_PREEMPT_NOTIFIER is selected in your .config.  You'll
> have to adjust Kconfig or select the in-tree kvm for that.

Is there a possibility to check, if CONFIG_PREEMPT_NOTIFIER correct selected and compiled in the kernel/modules? 

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Re: KVM and Prempt?

[Avi Kivity]

Back, Michael (ext) wrote:
>>>   
>>>       
>> Make sure CONFIG_PREEMPT_NOTIFIER is selected in your .config.  You'll
>> have to adjust Kconfig or select the in-tree kvm for that.
>>     
>
> Is there a possibility to check, if CONFIG_PREEMPT_NOTIFIER correct selected and compiled in the kernel/modules? 
>   

The external module code checks CONFIG_PREEMPT_NOTIFIER, and emulates 
preempt notifiers if not present in the host kernel.  But the preempt 
notifier emulation has not been tested with -rt and may be broken there.

-- 
error compiling committee.c: too many arguments to function


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Re: KVM and Prempt?

[Back, Michael (ext)]

 

> -----Ursprüngliche Nachricht-----
> Von: Avi Kivity [mailto:avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org] 
> Gesendet: Monday, October 22, 2007 1:52 PM
> An: Back, Michael (ext)
> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> Betreff: Re: AW: [kvm-devel] KVM and Prempt?
> 
> Back, Michael (ext) wrote:
> >>>   
> >>>       
> >> Make sure CONFIG_PREEMPT_NOTIFIER is selected in your 
> .config.  You'll
> >> have to adjust Kconfig or select the in-tree kvm for that.
> >>     
> >
> > Is there a possibility to check, if CONFIG_PREEMPT_NOTIFIER 
> correct selected and compiled in the kernel/modules? 
> >   
> 
> The external module code checks CONFIG_PREEMPT_NOTIFIER, and emulates 
> preempt notifiers if not present in the host kernel.  But the preempt 
> notifier emulation has not been tested with -rt and may be 
> broken there.
> 

Greate now it works on Intel!
Now CONFIG_PREEMPT_NOTIFIERS in my .config and I used the newerst KVM (48).
My next test is on AMD - mybe it works too!?

Thanks
Michael

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Re: KVM and Prempt?

[Back, Michael (ext)]

With the CONFIG_PREEMPT_NOTIFIERS=y (Kconfig modification) and kvm-48 it works on AMD too!

Only the smp-option doesn't work korrect, but this is no problem for my tests :-)

Thanks for help!

With best regards,
Michael


> -----Ursprüngliche Nachricht-----
> Von: Gregory Haskins [mailto:ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org] 
> Gesendet: Friday, October 19, 2007 5:27 PM
> An: Back, Michael (ext)
> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> Betreff: Re: AW: [kvm-devel] KVM and Prempt?
> 
> On Fri, 2007-10-19 at 16:17 +0200, Back, Michael (ext) wrote:
> 
> > >Are you referring to the -rt patch?
> > 
> > Yes, I take the patch from
> > http://www.kernel.org/pub/linux/kernel/projects/rt/
> > 
> 
> Ah, yes.  There were problems in the past with running KVM on 
> -rt if you
> have the full kit enabled.  Its possible they are still not fixed.
> 
> I had patches to address this issue for an older KVM and had it up and
> running on a full PREEMPT_RT kernel, but they have become 
> quite stale at
> this point.  I will be picking up this work again sometime in the near
> future, so watch this space.
> 
> Are you building KVM as a module from the -rt tree, or as an external
> module?
> 
> -Greg
> 

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KVM and Prempt?

[Back, Michael (ext)]

Hallo,
I tried to run Windows XP with KVM on Linux 2.6.31.1 on a 
AMD Opteron and on a Intel Xeon, on both it works fine!

After this test I patch the kernel with the current prempt-patch and on
both it doesn't works! 
-> After a very short time - I could see the windows startup screen -
the complied system froze!
 
Has you ever tried to do the same and it works?
Or will KVM with Windows on a prempt kernel 
- never work?
- maybe work in the future?
- should now work but this .. and this ... should be done and consider?

With best regards,
Michael

Re: KVM and Prempt?

[Sven-Thorsten Dietrich]

On Mon, 2007-10-22 at 09:01 +0200, Back, Michael (ext) wrote:
> Hallo,
> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a 

You mean .21.1 ? 

> AMD Opteron and on a Intel Xeon, on both it works fine!

> After this test I patch the kernel with the current prempt-patch and on
> both it doesn't works! 

Did you try against 2.6.23-rt1.

If you must stay on .21, you might have some other issues with the AMD
and NUMA.

At the very least, you will need to apply the attached patch from git
somehow, although this patch is against a new scheduler post 2.6.22, so
good luck :)

Sven

> -> After a very short time - I could see the windows startup screen -
> the complied system froze!
>  
> Has you ever tried to do the same and it works?
> Or will KVM with Windows on a prempt kernel 
> - never work?
> - maybe work in the future?
> - should now work but this .. and this ... should be done and consider?
> 
> With best regards,
> Michael
> -
> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html




diff-tree e107be36efb2a233833e8c9899039a370e4b2318 (from b47e8608a08766ef8121cd747d3aaf6c3dc22649)
Author: Avi Kivity <avi@qumranet.com>
Date:   Thu Jul 26 13:40:43 2007 +0200

    [PATCH] sched: arch preempt notifier mechanism
    
    This adds a general mechanism whereby a task can request the scheduler to
    notify it whenever it is preempted or scheduled back in.  This allows the
    task to swap any special-purpose registers like the fpu or Intel's VT
    registers.
    
    Signed-off-by: Avi Kivity <avi@qumranet.com>
    [ mingo@elte.hu: fixes, cleanups ]
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index d0926d6..484988e 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -8,6 +8,7 @@
 
 #include <linux/thread_info.h>
 #include <linux/linkage.h>
+#include <linux/list.h>
 
 #ifdef CONFIG_DEBUG_PREEMPT
   extern void fastcall add_preempt_count(int val);
@@ -60,4 +61,47 @@ do { \
 
 #endif
 
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+
+struct preempt_notifier;
+
+/**
+ * preempt_ops - notifiers called when a task is preempted and rescheduled
+ * @sched_in: we're about to be rescheduled:
+ *    notifier: struct preempt_notifier for the task being scheduled
+ *    cpu:  cpu we're scheduled on
+ * @sched_out: we've just been preempted
+ *    notifier: struct preempt_notifier for the task being preempted
+ *    next: the task that's kicking us out
+ */
+struct preempt_ops {
+	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
+	void (*sched_out)(struct preempt_notifier *notifier,
+			  struct task_struct *next);
+};
+
+/**
+ * preempt_notifier - key for installing preemption notifiers
+ * @link: internal use
+ * @ops: defines the notifier functions to be called
+ *
+ * Usually used in conjunction with container_of().
+ */
+struct preempt_notifier {
+	struct hlist_node link;
+	struct preempt_ops *ops;
+};
+
+void preempt_notifier_register(struct preempt_notifier *notifier);
+void preempt_notifier_unregister(struct preempt_notifier *notifier);
+
+static inline void preempt_notifier_init(struct preempt_notifier *notifier,
+				     struct preempt_ops *ops)
+{
+	INIT_HLIST_NODE(&notifier->link);
+	notifier->ops = ops;
+}
+
+#endif
+
 #endif /* __LINUX_PREEMPT_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7c61b50..7a4de87 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -935,6 +935,11 @@ struct task_struct {
 	struct sched_class *sched_class;
 	struct sched_entity se;
 
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+	/* list of struct preempt_notifier: */
+	struct hlist_head preempt_notifiers;
+#endif
+
 	unsigned short ioprio;
 #ifdef CONFIG_BLK_DEV_IO_TRACE
 	unsigned int btrace_seq;
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index c64ce9c..6b06663 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -63,3 +63,6 @@ config PREEMPT_BKL
 	  Say Y here if you are building a kernel for a desktop system.
 	  Say N if you are unsure.
 
+config PREEMPT_NOTIFIERS
+	bool
+
diff --git a/kernel/sched.c b/kernel/sched.c
index 93cf241..e901aa5 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1592,6 +1592,10 @@ static void __sched_fork(struct task_str
 	INIT_LIST_HEAD(&p->run_list);
 	p->se.on_rq = 0;
 
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+	INIT_HLIST_HEAD(&p->preempt_notifiers);
+#endif
+
 	/*
 	 * We mark the process as running here, but have not actually
 	 * inserted it onto the runqueue yet. This guarantees that
@@ -1673,6 +1677,63 @@ void fastcall wake_up_new_task(struct ta
 	task_rq_unlock(rq, &flags);
 }
 
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+
+/**
+ * preempt_notifier_register - tell me when current is being being preempted
+ *                         and rescheduled
+ */
+void preempt_notifier_register(struct preempt_notifier *notifier)
+{
+	hlist_add_head(&notifier->link, &current->preempt_notifiers);
+}
+EXPORT_SYMBOL_GPL(preempt_notifier_register);
+
+/**
+ * preempt_notifier_unregister - no longer interested in preemption notifications
+ *
+ * This is safe to call from within a preemption notifier.
+ */
+void preempt_notifier_unregister(struct preempt_notifier *notifier)
+{
+	hlist_del(&notifier->link);
+}
+EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
+
+static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
+{
+	struct preempt_notifier *notifier;
+	struct hlist_node *node;
+
+	hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
+		notifier->ops->sched_in(notifier, raw_smp_processor_id());
+}
+
+static void
+fire_sched_out_preempt_notifiers(struct task_struct *curr,
+				 struct task_struct *next)
+{
+	struct preempt_notifier *notifier;
+	struct hlist_node *node;
+
+	hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
+		notifier->ops->sched_out(notifier, next);
+}
+
+#else
+
+static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
+{
+}
+
+static void
+fire_sched_out_preempt_notifiers(struct task_struct *curr,
+				 struct task_struct *next)
+{
+}
+
+#endif
+
 /**
  * prepare_task_switch - prepare to switch tasks
  * @rq: the runqueue preparing to switch
@@ -1685,8 +1746,11 @@ void fastcall wake_up_new_task(struct ta
  * prepare_task_switch sets up locking and calls architecture specific
  * hooks.
  */
-static inline void prepare_task_switch(struct rq *rq, struct task_struct *next)
+static inline void
+prepare_task_switch(struct rq *rq, struct task_struct *prev,
+		    struct task_struct *next)
 {
+	fire_sched_out_preempt_notifiers(prev, next);
 	prepare_lock_switch(rq, next);
 	prepare_arch_switch(next);
 }
@@ -1728,6 +1792,7 @@ static inline void finish_task_switch(st
 	prev_state = prev->state;
 	finish_arch_switch(prev);
 	finish_lock_switch(rq, prev);
+	fire_sched_in_preempt_notifiers(current);
 	if (mm)
 		mmdrop(mm);
 	if (unlikely(prev_state == TASK_DEAD)) {
@@ -1768,7 +1833,7 @@ context_switch(struct rq *rq, struct tas
 {
 	struct mm_struct *mm, *oldmm;
 
-	prepare_task_switch(rq, next);
+	prepare_task_switch(rq, prev, next);
 	mm = next->mm;
 	oldmm = prev->active_mm;
 	/*
@@ -6335,6 +6400,10 @@ void __init sched_init(void)
 
 	set_load_weight(&init_task);
 
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+	INIT_HLIST_HEAD(&init_task.preempt_notifiers);
+#endif
+
 #ifdef CONFIG_SMP
 	nr_cpu_ids = highest_cpu + 1;
 	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);

Re: KVM and Prempt?

[Jan Kiszka]

Sven-Thorsten Dietrich wrote:
> On Mon, 2007-10-22 at 09:01 +0200, Back, Michael (ext) wrote:
>> Hallo,
>> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a 
> 
> You mean .21.1 ? 

Classic typo I interestingly also did several times the last week. :)

> 
>> AMD Opteron and on a Intel Xeon, on both it works fine!
> 
>> After this test I patch the kernel with the current prempt-patch and on
>> both it doesn't works! 
> 
> Did you try against 2.6.23-rt1.

kvm in -rt1 is not usable. It's too old, lacking PREEMPT_NOTIFIER
support, thus quickly triggering lockdep.

> 
> If you must stay on .21, you might have some other issues with the AMD
> and NUMA.
> 
> At the very least, you will need to apply the attached patch from git
> somehow, although this patch is against a new scheduler post 2.6.22, so
> good luck :)

<--snip-->

Those patches are already mainline... :->

What you rather need are latest kvm patches, or - if building the kvm
distribution out of tree - a patch to enabled CONFIG_PREEMPT_NOTIFIERS
unconditionally:

--- linux-2.6.23.1-rt/kernel/Kconfig.preempt.orig
+++ linux-2.6.23.1-rt/kernel/Kconfig.preempt
@@ -136,6 +136,7 @@

 config PREEMPT_NOTIFIERS
 	bool
+	default y

 config PREEMPT_BKL
 	bool


Still, I'm seeing oopses here (more precisely, lock validator
complaints), but I need to re-test, better using kvm from git instead of
kvm-48.

Beyond this, I'm struggling to understand 300-400 us vm-exit latencies
(over Intel VMX), which appear to be independent of the underlying
system. See kvm-devel. Such latencies would limit the RT usability of
kvm - unless you spent dedicated CPUs.

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

Re: KVM and Prempt?

[Gregory Haskins]

[-- Attachment #1: Type: text/plain, Size: 2212 bytes --]

On Tue, 2007-10-23 at 10:35 +0200, Jan Kiszka wrote:
> Sven-Thorsten Dietrich wrote:
> > On Mon, 2007-10-22 at 09:01 +0200, Back, Michael (ext) wrote:
> >> Hallo,
> >> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a 
> > 
> > You mean .21.1 ? 
> 
> Classic typo I interestingly also did several times the last week. :)
> 
> > 
> >> AMD Opteron and on a Intel Xeon, on both it works fine!
> > 
> >> After this test I patch the kernel with the current prempt-patch and on
> >> both it doesn't works! 
> > 
> > Did you try against 2.6.23-rt1.
> 
> kvm in -rt1 is not usable. It's too old, lacking PREEMPT_NOTIFIER
> support, thus quickly triggering lockdep.
> 
> > 
> > If you must stay on .21, you might have some other issues with the AMD
> > and NUMA.
> > 
> > At the very least, you will need to apply the attached patch from git
> > somehow, although this patch is against a new scheduler post 2.6.22, so
> > good luck :)
> 
> <--snip-->
> 
> Those patches are already mainline... :->
> 
> What you rather need are latest kvm patches, or - if building the kvm
> distribution out of tree - a patch to enabled CONFIG_PREEMPT_NOTIFIERS
> unconditionally:
> 
> --- linux-2.6.23.1-rt/kernel/Kconfig.preempt.orig
> +++ linux-2.6.23.1-rt/kernel/Kconfig.preempt
> @@ -136,6 +136,7 @@
> 
>  config PREEMPT_NOTIFIERS
>  	bool
> +	default y
> 
>  config PREEMPT_BKL
>  	bool
> 
> 
> Still, I'm seeing oopses here (more precisely, lock validator
> complaints), but I need to re-test, better using kvm from git instead of
> kvm-48.
> 
> Beyond this, I'm struggling to understand 300-400 us vm-exit latencies
> (over Intel VMX), which appear to be independent of the underlying
> system. See kvm-devel. Such latencies would limit the RT usability of
> kvm - unless you spent dedicated CPUs.

Some work is still left to be done in this area.  Until then you will
see problems like you are describing.

At one point I had a patch series that allowed KVM to actually work in
-rt without crashes, and with decent latencies (both host, and guest).
Some point soon I will revive the series and port it to the latest
kvm.git.

HTH

Regards,
-Greg



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KVM and Prempt?

[Back, Michael (ext)]

[-- Attachment #1.1: Type: text/plain, Size: 1781 bytes --]


Hallo,
I tried to run Windows XP with KVM on Linux 2.6.31.1 on a AMD Opteron and on a Intel Xeon, on both it works fine!

After this test I patch the kernel with the current prempt-patch and on both it doesn't works!
-> After a very short time - I could see the windows startup screen - the complied system froze!

Has someone ever tried to do the same and it works?
Or will KVM with Windows on a prempt kernel 
- never work?
- maybe work in the future?
- should now work but this .. and this ... should be done and consider?

With best regards,
Michael Back

#########################
ASTRUM IT GmbH 
Michael Back

Dipl.-Ing. Univ. 
software engineer
Projectmanagement

Am Wolfsmantel 46
91058 Erlangen, Germany 
Tel.: +49 (91 31) 94 08 - 374 
Fax: +49 (91 31) 94 08 - 108 
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contact address by Siemens 
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Allee am Roethelheimpark 2
91052 Erlangen, Germany
Tel.: +49 (9131) 84-5307
Fax: +49 (9131) 84-8767
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