[PATCH] libxl: Fix domain startup failure error reporting

Cole Robinson crobinso at redhat.com
Tue Jun 21 13:03:12 UTC 2022


On 6/21/22 3:55 AM, Michal Prívozník wrote:
> On 6/17/22 23:29, Cole Robinson wrote:
>> When domain startup fails, domain cleanup calls
>> libxlNetworkUnwindDevices, which calls virGetConnectNetwork, which
>> is a top level API entry point, which resets the initial saved error,
>> leading to clients seeing:
>>
>>   error: An error occurred, but the cause is unknown
>>
>> This preserves the error from before virGetConnectNetwork is called.
>>
>> Signed-off-by: Cole Robinson <crobinso at redhat.com>
>> ---
>>  src/libxl/libxl_domain.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
>> index 17b347de4e..bda110e9e6 100644
>> --- a/src/libxl/libxl_domain.c
>> +++ b/src/libxl/libxl_domain.c
>> @@ -830,12 +830,17 @@ libxlNetworkUnwindDevices(virDomainDef *def)
>>              /* cleanup actual device */
>>              virDomainNetRemoveHostdev(def, net);
>>              if (net->type == VIR_DOMAIN_NET_TYPE_NETWORK) {
>> -                g_autoptr(virConnect) conn = virGetConnectNetwork();
>> +                g_autoptr(virConnect) conn = NULL;
>> +                virErrorPtr save_err;
>> +
>> +                virErrorPreserveLast(&save_err);
>> +                conn = virGetConnectNetwork();
>>  
>>                  if (conn)
>>                      virDomainNetReleaseActualDevice(conn, def, net);
>>                  else
>>                      VIR_WARN("Unable to release network device '%s'", NULLSTR(net->ifname));
>> +                virErrorRestore(&save_err);
>>              }
>>          }
>>      }
> 
> This fixes this particular function. I wonder whether we should mimic
> what QEMU driver does and wrap whole qemuProcessShutdown(), I mean
> libxlDomainCleanup() in virErrorPreserveLast(). Something like this:
> 
> diff --git i/src/libxl/libxl_domain.c w/src/libxl/libxl_domain.c
> index bda110e9e6..8e8ddd284a 100644
> --- i/src/libxl/libxl_domain.c
> +++ w/src/libxl/libxl_domain.c
> @@ -908,10 +908,13 @@ libxlDomainCleanup(libxlDriverPrivate *driver,
>      virHostdevManager *hostdev_mgr = driver->hostdevMgr;
>      unsigned int hostdev_flags = VIR_HOSTDEV_SP_PCI;
>      size_t i;
> +    virErrorPtr save_err;
>  
>      VIR_DEBUG("Cleaning up domain with id '%d' and name '%s'",
>                vm->def->id, vm->def->name);
>  
> +    virErrorPreserveLast(&save_err);
> +
>      hostdev_flags |= VIR_HOSTDEV_SP_USB;
>  
>      /* Call hook with stopped operation. Ignore error and continue with cleanup */
> @@ -984,6 +987,7 @@ libxlDomainCleanup(libxlDriverPrivate *driver,
>                                      VIR_HOOK_SUBOP_END, NULL));
>  
>      virDomainObjRemoveTransientDef(vm);
> +    virErrorRestore(&save_err);
>  }
>  
>  /*
> @@ -1245,6 +1249,7 @@ libxlDomainStartPrepare(libxlDriverPrivate *driver,
>  {
>      virHostdevManager *hostdev_mgr = driver->hostdevMgr;
>      unsigned int hostdev_flags = VIR_HOSTDEV_SP_PCI | VIR_HOSTDEV_SP_USB;
> +    virErrorPtr save_err;
>  
>      if (virDomainObjSetDefTransient(driver->xmlopt, vm, NULL) < 0)
>          return -1;
> @@ -1272,10 +1277,12 @@ libxlDomainStartPrepare(libxlDriverPrivate *driver,
>      return 0;
>  
>   error:
> +    virErrorPreserveLast(&save_err);
>      libxlNetworkUnwindDevices(vm->def);
>      virHostdevReAttachDomainDevices(hostdev_mgr, LIBXL_DRIVER_INTERNAL_NAME,
>                                      vm->def, hostdev_flags);
>      virDomainObjRemoveTransientDef(vm);
> +    virErrorRestore(&save_err);
>      return -1;
>  }
>  
> 
> If this works, replace your patch with this diff, apply my:
> 
> Reviewed-by: Michal Privoznik <mprivozn at redhat.com>

Thanks, I made that change and pushed now

- Cole


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