Re: [Xen-devel] [PATCH v5 5/7] libxl: allow creation of domains with a specified or random domid

From: Ian Jackson <ian.jackson@citrix.com>
To: "Durrant, Paul" <pdurrant@amazon.co.uk>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien@xen.org>, Wei Liu <wl@xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Andrew Cooper <Andrew.Cooper3@citrix.com>,
	Jason Andryuk <jandryuk@gmail.com>,
	George Dunlap <George.Dunlap@citrix.com>,
	Jan Beulich <jbeulich@suse.com>,
	Anthony Perard <anthony.perard@citrix.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [Xen-devel] [PATCH v5 5/7] libxl: allow creation of domains with a specified or random domid
Date: Tue, 18 Feb 2020 11:17:08 +0000	[thread overview]
Message-ID: <24139.51124.66017.255351@mariner.uk.xensource.com> (raw)
In-Reply-To: <78ccdd687a344eaf92ed8c978dc04f3c@EX13D32EUC003.ant.amazon.com>

Durrant, Paul writes ("RE: [PATCH v5 5/7] libxl: allow creation of domains with a specified or random domid"):
> No, the domain will not be leaked. The existing failure handling in libxl will clean up if *domid != INVALID_DOMID.

Sorry if I was confused; I will read this again.

> > > diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> > > index d2198dffad..75b1619d0d 100644
> > > --- a/xen/include/public/xen.h
> > > +++ b/xen/include/public/xen.h
> > > @@ -614,6 +614,9 @@ DEFINE_XEN_GUEST_HANDLE(mmuext_op_t);
> > >  /* Idle domain. */
> > >  #define DOMID_IDLE           xen_mk_uint(0x7FFF)
> > >
> > > +/* Mask for valid domain id values */
> > > +#define DOMID_MASK           xen_mk_uint(0x7FFF)
> > 
> > This needs a hypervisor maintainer ack.
> > 
> > Please split it into its own patch, with a rationale, etc.
> 
> Ok, but it has no rationale without the rest of this patch; I can only assert that it 'will be needed by a subsequent patch'.

What do the Xen maintainers, and my tools co-maintainers think ?

I was hoping for a rationale along the lines of:

  This is useful for programs which need to [explanation],
  including for example, libxl, which is going to want to
  randomly generate domids.

Maybe it needs some explanation of why this belongs in the Xen public
headers rather than in some header available to libxc, libxl and other
tools stuff ?

Ian.

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