Re: [Xen-devel] [PATCH 0/3] tools: support autoballooning of xenstore domain

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

Juergen Gross writes ("[PATCH 0/3] tools: support autoballooning of xenstore 
domain"):
> Support xenstore domain autoballooning by:
> - adding --maxmem parameter to init-xenstore-domain
> - build xenstore stubdom with Mini-OS CONFIG_BALLOON set
> - add XENSTORE_MAX_DOMAIN_SIZE parameter to sysconfig.xencommons
> 
> This series requires Mini-OS ballooning support, of course. I'm posting
> it now because this will make it easier to test my Mini-OS series.

The basic idea seems sound enough, and I didn't spot much wrong with
the implementation, although I have some questions/observations:

 * AFAICT this is going to take effect for C xenstored.  But ISTM that
   we probably want to be moving away from C xenstored; its code is
   difficult, it has a history of hard to fathom bugs, and I'm
   concerned about its security properties.

 * I find that the pointer-arithmetic-based parsing style (as seen in
   patch 1) very hard to read.  I haven't reviewed it.  But I think it
   is not exposed to untrusted input so I don't think I care.

 * If we are going in this direction, this feature probably wants to
   be enabled by default.  Do you have a good idea of default
   parameters ?

Thanks,
Ian.

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