Re: [Xen-devel] [PATCH 2/2] xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches from old kernel

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2011-09-22 at 15:14 +0100, Olaf Hering wrote:
> Add new xs_reset_watches function to shutdown watches from old kernel after
> kexec boot.  The old kernel does not unregister all watches in the
> shutdown path.  They are still active, the double registration can not
> be detected by the new kernel.  When the watches fire, unexpected events
> will arrive and the xenwatch thread will crash (jumps to NULL).  An
> orderly reboot of a hvm guest will destroy the entire guest with all its
> resources (including the watches) before it is rebuilt from scratch, so
> the missing unregister is not an issue in that case.
> 
> With this change the xenstored is instructed to wipe all active watches
> for the guest.  However, a patch for xenstored is required so that it
> accepts the XS_RESET_WATCHES request from a client (see changeset
> 23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
> the registration of watches will fail and some features of a PVonHVM
> guest are not available. The guest is still able to boot, but repeated
> kexec boots will fail.

This appears to break with oxenstored. It just hangs waiting for a
response from the daemon.

I suspect it is a bug in the daemon if it doesn't respond with an
appropriate error for an unknown command. I'll see if I can figure out
what is going wrong.

Ian.


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