Re: [Xen-devel] [PATCH] tools/xend: Only add cpuid and cpuid_check to sexpr once

[Olaf Hering <olaf@xxxxxxxxx>]

On Tue, Feb 19, Ian Jackson wrote:

> Olaf Hering writes ("[Xen-devel] [PATCH] tools/xend: Only add cpuid and 
> cpuid_check to sexpr once"):
> > tools/xend: Only add cpuid and cpuid_check to sexpr once
> > 
> > When converting a XendConfig object to sexpr, cpuid and cpuid_check
> > were being emitted twice in the resulting sexpr.  The first conversion
> > writes incorrect sexpr, causing parsing of the sexpr to fail when xend
> > is restarted and domain sexpr files in /var/lib/xend/domains/<dom-uuid>
> > are read and parsed.
> > 
> > This patch skips the first conversion, and uses only the custom
> > cpuid{_check} conversion methods called later.  It is not pretty, but
> > is the least invasive fix in this complex code.
> 
> We do intend to fix bugs in xend, but I'm worried that this change
> might break something.  I don't know the code at all so forgive me if
> I'm asking stupid questions, but why does the first conversion emit an
> invalid sexpr ?

The result of having cpuid= in the domU.cfg and doing a rcxend restart is
that the sxp string is not properly converted into a list and dict(?),
instead the string is partly passed as is. xend will reject the sxp and
the domU disappears until its readded with xm new.

This change has been used almost a year now in production, no errors
were reported.

Olaf

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