Re: [Xen-devel] [PATCH] Prevent changing a memory size of Domain-0 even if users make a careless mistake

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I think it's fair to just say "Don't do that then, you idiot!". :-)

I think if we have a "dom0-min-mem" parameter then we may as well use it 
consistently.  We already use it to prevent event quite determined 
foot-shooting attempts (like starting up too many domains!).

Seems consistent to apply the rule whenever an xm command might balloon dom0.

Kan, a comment on your patch:


diff -r db943e8d1051 tools/python/xen/xend/XendDomainInfo.py
--- a/tools/python/xen/xend/XendDomainInfo.py   Tue Apr 01 10:09:33 2008 +0100
+++ b/tools/python/xen/xend/XendDomainInfo.py   Fri Apr 04 13:43:55 2008 +0900
@@ -986,6 +986,14 @@ class XendDomainInfo:
                   self.info['name_label'], str(self.domid), target)
         
         MiB = 1024 * 1024
+
+        if self.domid == 0:
+            dom0_min_mem = xoptions.get_dom0_min_mem()
+            memory_cur = self.get_memory_dynamic_max() / MiB
+            if target < memory_cur:
+                if dom0_min_mem == 0 or dom0_min_mem > target:

If I recall correctly, the current meaning of dom0_min_mem set to 0 is "No 
limiting", so I think you can just remove that check to be consistent with 
existing behaviour.

Cheers,
Mark

+                    raise XendError("memory_dynamic_max cannot be changed for 
safety reasons")
+
         self._safe_set_memory('memory_dynamic_min', target * MiB)
         self._safe_set_memory('memory_dynamic_max', target * MiB)
 


>  -- Keir
>
> On 4/4/08 11:06, "Masaki Kanno" <kanno.masaki@xxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > If users accidentally change a memory size of Domain-0 to very small
> > memory size by xm mem-set command, users will be not able to operate
> > Domain-0.  I think that Domain-0 is important for Xen, so I'd like to
> > prevent the accident by xm mem-set command.
> >
> > This patch prevents changing the memory size of Domain-0 by xm mem-set
> > command if specified memory size is smaller than dom0-min-mem in
> > xend-config.sxp.
> >
> >  # cat /etc/xen/xend-config.sxp | grep "(dom0-min-mem"
> >  (dom0-min-mem 384)
> >  # xm list Domain-0
> >  Name                                        ID   Mem VCPUs      State
> > Time(s)
> >  Domain-0                                     0   941     2     r-----
> > 62.6
> >  # xm mem-set Domain-0 1
> >  Error: memory_dynamic_max cannot be changed for safety reasons
> >  Usage: xm mem-set <Domain> <Mem>
> >
> >  Set the current memory usage for a domain.
> >  # xm list Domain-0
> >  Name                                        ID   Mem VCPUs      State
> > Time(s)
> >  Domain-0                                     0   941     2     r-----
> > 63.6
> >
> >
> > Signed-off-by: Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>
> >
> > Best regards,
> >  Kan
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



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