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

[Jiri Denemark]

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:
> > > Let libvirtd handle invalid x86 cpu map error, and report the real reason.
> > > 
> > > This issue can be reproduced :
> > > 1, rm -rf /share/libvirt/cpu_map
> > > 2, start libvirtd
> > > 3, virsh create INSTANCE.xml
> > > 
> > > Libvirtd reports error :
> > > error: invalid argument: Failed to parse group 'tss'
> > > 
> > > In face, libvirtd gets invalid cpu map.
> > > With this patch, libvirtd reports error :
> > > error: unsupported configuration: invalid x86 cpu map
> > > 
> > > Signed-off-by: zhenwei pi <pizhenwei at bytedance.com>
> > > ---
> > >  src/cpu/cpu_x86.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
> > > index d3a88da21d..91419d91d4 100644
> > > --- a/src/cpu/cpu_x86.c
> > > +++ b/src/cpu/cpu_x86.c
> > > @@ -2902,8 +2902,11 @@ virCPUx86ValidateFeatures(virCPUDefPtr cpu)
> > >      virCPUx86MapPtr map;
> > >      size_t i;
> > >  
> > > -    if (!(map = virCPUx86GetMap()))
> > > +    if (!(map = virCPUx86GetMap())) {
> > > +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> > > +                        _("invalid x86 cpu map"));
> > >          return -1;
> > > +    }
> > 
> > This is definitely not the right place to fix the issue. virCPUx86GetMap
> > is called from a lot of places and your patch would only fix one of
> > them. Moreover the message itself is not very helpful as it doesn't say
> > why the CPU map is invalid. The right solution would be to show the
> > error reported from virCPUx86LoadMap. However, it is called inside
> > virCPUx86DriverOnceInit, which is only called once per libvirtd life
> > time. I think you'd need to store that error and reuse it everytime
> > cpuMap is NULL inside virCPUx86GetMap.
> 
> VIR_ONCE_GLOBAL_INIT already keeps a record of errors raised in the
> initializer & re-raises them

Eh, good to know :-) Anyway, it seems it doesn't really work and mostly
some random unrelated error is reported. In my case I see

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.

Jirka