[libvirt] [PATCH] report invalid x86 cpu map error

[Peter Krempa]

On Tue, Jan 15, 2019 at 15:42:41 +0100, Jiri Denemark wrote:
> On Mon, Jan 14, 2019 at 15:40:32 +0000, Daniel P. Berrangé wrote:
> > On Mon, Jan 14, 2019 at 04:15:01PM +0100, Jiri Denemark wrote:
> > > On Mon, Jan 14, 2019 at 15:03:26 +0000, Daniel P. Berrangé wrote:
> > > > On Mon, Jan 14, 2019 at 03:36:38PM +0100, Jiri Denemark wrote:
> > > > > On Mon, Jan 14, 2019 at 14:21:42 +0000, Daniel P. Berrangé wrote:
> > > > > > On Mon, Jan 14, 2019 at 02:56:43PM +0100, Jiri Denemark wrote:
> > > > > > > On Mon, Jan 14, 2019 at 20:07:34 +0800, zhenwei pi wrote:

[...]

> > > > > virsh # cpu-models x86_64
> > > > > error: failed to get CPU model names
> > > > > error: Storage volume not found: no storage vol with matching path
> > > > > '/vm/systemrescuecd-x86-2.5.1.iso'
> > > > > 
> > > > > So there's definitely a bug to be fixed somewhere.
> > > > 
> > > > Hmm, what steps did you use to get into that situation ?  It works as
> > > > expected for me, re-reporting the original error.
> > > 
> > > I just moved away the CPU map file. But it appears I have a domain
> > > defined pointing to a non-existent disk image. It seems the problem
> > > shows up when multiple errors are raised when libvirtd is starting up.
> > 
> > Can you elaborate on that - what guest  & storage pool config do you
> > have.  I'm struggling to see how to exercise the codepath that reports
> > that error during startup.
> 
> While I had a domain pointing to an inexistent disk image, it did not
> actually cause the strange error reported by virCPUx86GetMap. This is
> what caused the error to be reported: I have a directory storage pool in
> /vm, which is autostarted on libvirtd startup. That directory contained
> sysres1.qcow file with systemrescuecd-x86-2.5.1.iso backing file. But
> the backing file was missing. The storage driver refreshes all active
> pools and once it gets to sysres1.qcow, virStorageBackendVolOpen fails
> with "Storage volume not found: no storage vol with matching path
> '/vm/systemrescuecd-x86-2.5.1.iso'".

And the code loading the map ends up calling virXMLParseHelper() which
calls xmlCtxtReadFile. On failure it jumps to the 'error' label with the
following code:

    if (virGetLastErrorCode() == VIR_ERR_OK) {
        virGenericReportError(domcode, VIR_ERR_XML_ERROR,
                              _("failed to parse xml document '%s'"),
                              filename ? filename : "[inline data]");
    }

So it looks like the previous error was not cleared and thus the XML
parser does not raise it's own error.

The error then gets remembered forever in the virOnce infrastructure
which actually works as intended.

I'm not sure whether there's any sane reason for the XML parser to avoid
overwriting an error.
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