Re: [Xen-devel] [PATCH v3 00/18] libxl: domain save/restore: run in a separate process [and 4 more messages]

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

To: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Cc: "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH v3 00/18] libxl: domain save/restore: run in
 a separate process
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Ian Campbell writes ("Re: [Xen-devel] [PATCH v3 00/18] libxl: domain 
save/restore: run in a separate process"):
> On Fri, 2012-06-08 at 18:34 +0100, Ian Jackson wrote:
> > This is v3 of my series to asyncify save/restore, rebased to current
> > tip, retested, and with all comments addressed.
> 
> There's quite a lot of combinations which need testing here (PV, HVM,
> HVM w/ stub dm, old vs new qemu etc etc), which of those have you tried?
> 
> I tried a simple localhost migrate of a PV guest and:

Thanks for looking at all this and for testing it.  I thought I had
tested localhost migration, but my shell history reveals, now that it
is pointed out to me, that in my tests the migration receiver process
had been running the old version of libxl.

Ian Campbell writes ("Re: [Xen-devel] [PATCH v3 00/18] libxl: domain 
save/restore: run in a separate process"):
> The first zero here is restore_fd, I think. But I read in the comment in
> the helper:
>         > + * The helper talks on stdin and stdout, in binary in machine
>         > + * endianness.  The helper speaks first, and only when it has a
>         > + * callback to make.  It writes a 16-bit number being the message
>         > + * length, and then the message body.
> 
> So restore_fd == stdin => running two protocols over the same fd?

This is indeed why it's not working.  I have repro'd the failure and
my tree now has a fix in it.

Ian Campbell writes ("Re: [Xen-devel] [PATCH v3 00/18] libxl: domain 
save/restore: run in a separate process"):
> Oh, right, migrate-receive takes the migration fd on stdin doesn't it,
> so that's where it comes from. I still suspect it is wrong. Might need
> to dup the input onto a safe fd?

Indeed.

> BTW, since I've been ctrl-c'ing "xl migrate" a bunch I noticed that we
> seem to leak an "xl migrate-receive" and the restore side helper
> process. Probably pre-existing but I thought it worth mentioning.

I'll look into this.

Thanks,
Ian.

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