Re: [Xen-devel] [PATCH 3 of 3] VM generation ID save/restore and migrate

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2011-12-16 at 12:51 +0000, Paul Durrant wrote:
> > -----Original Message-----
> > From: Ian Campbell
> > Sent: 16 December 2011 12:08
> > To: Paul Durrant
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] [PATCH 3 of 3] VM generation ID
> > save/restore and migrate
> > 
> > On Fri, 2011-12-16 at 11:47 +0000, Paul Durrant wrote:
> > > diff -r d44e885e0389 -r e745cfbe7e11
> > tools/python/xen/lowlevel/checkpoint/libcheckpoint.c
> > > --- a/tools/python/xen/lowlevel/checkpoint/libcheckpoint.c
> > Fri Dec 16 11:43:52 2011 +0000
> > > +++ b/tools/python/xen/lowlevel/checkpoint/libcheckpoint.c
> > Fri Dec 16 11:43:53 2011 +0000
> > > @@ -175,6 +175,7 @@ int checkpoint_start(checkpoint_state* s  {
> > >      int hvm, rc;
> > >      int flags = XCFLAGS_LIVE;
> > > +    unsigned long vm_generationid_addr;
> > >
> > >      if (!s->domid) {
> > >         s->errstr = "checkpoint state not opened"; @@ -185,16
> > +186,28
> > > @@ int checkpoint_start(checkpoint_state* s
> > >
> > >      hvm = s->domtype > dt_pv;
> > >      if (hvm) {
> > > +       char path[128];
> > > +       char *addr;
> > > +
> > > +       sprintf(path,
> > > + "/local/domain/%u/hvmloader/generation-id-address", s->domid);
> > 
> > xs_get_domain_path() gives you the correct base path (I saw at least
> > one more of these).
> > 
> 
> Does that save me anything?

Probably not much, other than avoiding hardcoding something. I
guess /local/domain/%d is fair game in a toolstack.

>  I'd end up having to
> 
> sprintf(path, "%s/hvmloader/generation-id-address", 
> xs_get_domain_path(s->xsh, s->domid))
> 
> since xs_read() just takes a path rather than a (prefix, node) couple.

xs_chdir() would actually be quite useful for this sort of thing, but it
doesn't exist so nevermind.

Ian.


> 
>   Paul
> 
> > > diff -r d44e885e0389 -r e745cfbe7e11 tools/xcutils/xc_restore.c
> > > --- a/tools/xcutils/xc_restore.c        Fri Dec 16 11:43:52 2011
> > +0000
> > > +++ b/tools/xcutils/xc_restore.c        Fri Dec 16 11:43:53 2011
> > +0000
> > [...]
> > > diff -r d44e885e0389 -r e745cfbe7e11 tools/xcutils/xc_save.c
> > > --- a/tools/xcutils/xc_save.c   Fri Dec 16 11:43:52 2011 +0000
> > > +++ b/tools/xcutils/xc_save.c   Fri Dec 16 11:43:53 2011 +0000
> > [...]
> > 
> > AFAIK these two are only used by xend so unless you are adding
> > support for this stuff there (it's deprecated so no need) this isn't
> > necessary, also I think xend reads the stdout of one or both and
> > you've added to what gets printed, running the risk of breaking
> > things.
> > 
> > Ian.
> > 
> 



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