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Re: [Xen-devel] xl save but leave domain paused

  • To: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
  • From: Ian Murray <murrayie@xxxxxxxxxxx>
  • Date: Sun, 9 Jun 2013 22:41:24 +0100 (BST)
  • Cc: "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>
  • Delivery-date: Sun, 09 Jun 2013 21:42:02 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

Thanks for reading and responding

> Does it work if you simply do the pause before the resume? Looking at
> the hypervisor side it appears that pauses are referenced counted and it
> looks (based on a cursory glance) that it will do the right thing.

I tried this before and it didn't seems to work. However, it seems to working 
now, having repeated the exercise.

From memory It seemed to leave the domain in either a "pss" or similar 
unhealthy state (I don't remember exactly). I have since discovered this may be 
a different issue around suspending/checkpointing using a CentOS 5.x Xen kernel 
and also I was working with a domain I broke because of experimentation.

Anyway, I will spend more time testing this solution.

>>   I have looked at the corresponding xc calls but meddling with 
>>  those is way beyond my knowledge. Another way of looking at the problem 
>>  would be able to perform an xl save on a paused domain, as this would 
>>  achieve the same result.
> OOI what happens if you try that?

As far as I remember it complained that the domain didn't respond to the 
suspend request. I was going to repeat the exercise but that seems like a moot 
point now.

>>  (Against RELEASE-4.2.2)
> FYI any eventual patch will need to be against unstable and then
> considered separately for backporting.

Sure. I just needed a working place to start.

If I was to prepare a patch against unstable, would it be accepted?

The code I ended up with was (which is what I think you expected):-

    if (leavepaused || checkpoint || rc < 0) {
        if (leavepaused && ! (rc < 0)) {
            libxl_domain_pause(ctx, domid);
            fprintf(stderr, "Pausing before resume\n");
        libxl_domain_resume(ctx, domid, 1, 0);
         libxl_domain_destroy(ctx, domid, 0);

> Ian.

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