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[Xen-devel] RE: [PATCH] avoid injection of missed timer interrupts while

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH] avoid injection of missed timer interrupts while debugging a guest
From: "Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>
Date: Wed, 19 Apr 2006 15:05:03 -0700
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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Thread-index: AcZj+P4lNFnPaFdlTtepHsfSz5r19AABBlNQ
Thread-topic: [PATCH] avoid injection of missed timer interrupts while debugging a guest
Hi Keir,
  Here is the patch for avoiding missing timer ticks injection for the
paused domain.

Signed-Off-by: Nitin A Kamble <nitin.a.kamble@xxxxxxxxx>

Thanks & Regards,
Open Source Technology Center, Intel Corp

>-----Original Message-----
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>Sent: Wednesday, April 19, 2006 2:31 PM
>To: Kamble, Nitin A
>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Ian Pratt
>Subject: Re: [PATCH] avoid injection of missed timer interrupts while
>debugging a guest
>On 19 Apr 2006, at 22:28, Kamble, Nitin A wrote:
>>   Gdbserver does use the xc_ptrace(PTRACE_ATTACH), and the
>> PTRACE_ATTACH uses xc_domain_pause() to pause the running guest for
>> debugging.
>>   This is the same interface called by "xm pause".
>> One more thing, the PIT missed timer ticks injection code is invoked
>> later after the domain is un-paused, so at the time of that
>> the domain is no more paused.
>>   I think what you are saying can be achieved by keeping a flag that
>> will tell the PIT code that the domain was paused & unpaused and so
>> you have missed ticks do not try to inject it.
>>   Did I understand you correctly, and do you think the
>> "domain_was_paused" flag is the right solution?
>Yes, you've got it. It is rather a pain as you note -- you essentially
>want a notifier on pause so the hvm code can maintain this flag that
>you can check-and-clear the next time you try to account missed ticks.
>On the other hand, a check for debugger mode is a bit gross and bizarre
>in the guts of HVM timer handling code. :-) I would at least like to
>see a patch that tries the more general approach and then we can pick
>between them.
>There is also the question of whether or not we do generally want to
>account missed ticks if a domain is paused for some reason. But I'm
>pretty sure the answer is 'no'.
>  -- Keir

Attachment: avoid_missed_ticks_on_domain_pause.patch
Description: avoid_missed_ticks_on_domain_pause.patch

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