[libvirt] [REPOST PATCHv2 1/2] qemu: Check for existing hostdev address for cold attach device

[Michal Privoznik]

On 07/13/2018 02:50 PM, John Ferlan wrote:
> 
> 
> On 07/09/2018 10:32 AM, Michal Privoznik wrote:
>> On 07/06/2018 08:50 PM, John Ferlan wrote:
>>> Prior to the hostdev being inserted in the hostdevs list,
>>> add a check during qemuDomainAttachDeviceConfig to determine
>>> whether the new/incoming <hostdev ...> device is providing
>>> the same <address> as some existing hostdev on the list
>>> and if so fail the cold attach.
>>>
>>> This cannot be done during virDomainHostdevDefPostParse
>>> because that is called after virDomainDefParseXML would
>>> have inserted a hostdev onto the hostdevs list and thus
>>> would have a "conflict" with itself. Therefore, the post
>>> parse processing can only compare if the current hostdev
>>> address conflicts with a SCSI <disk> address.
>>>
>>> By comparison this is similar to the validation phase
>>> checks in virDomainDefCheckDuplicateDriveAddresses that
>>> occur during define/startup processing but are not run
>>> during config attach of a live guest.
>>>
>>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>>> ---
>>>  src/qemu/qemu_driver.c | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>>> index 9a35e04a85..ef1abe3f68 100644
>>> --- a/src/qemu/qemu_driver.c
>>> +++ b/src/qemu/qemu_driver.c
>>> @@ -8007,6 +8007,12 @@ qemuDomainAttachDeviceConfig(virDomainDefPtr vmdef,
>>>                             _("device is already in the domain configuration"));
>>>              return -1;
>>>          }
>>> +        if (dev->data.hostdev->info->type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE &&
>>> +            virDomainDefHasDeviceAddress(vmdef, dev->data.hostdev->info)) {
>>> +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>>> +                           _("a device with the same address already exists "));
>>> +            return -1;
>>> +        }
>>>          if (virDomainHostdevInsert(vmdef, hostdev))
>>>              return -1;
>>>          dev->data.hostdev = NULL;
>>>
>>
>> I think hostdevs are not the only type of device suffering from this. In
>> fact, I've just tested disks and libvirt accepts attaching another disk
>> onto same <address/> happily.
>>
>> I wonder if this should go into virDomainDefCompatibleDevice() (now that
>> we have @action there ;-) ).
>>
> 
> It's a case of myopia for the bug I'm working on as listed in patch2.
> 
> What I did is no different than the VIR_DOMAIN_DEVICE_RNG check in the
> same function.
> 
> Still, if I change this patch to add:
> 
>      if (action == VIR_DOMAIN_DEVICE_ACTION_ATTACH && !live &&
> data.newInfo &&
>         data.newInfo->type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE &&
>         virDomainDefHasDeviceAddress(def, data.newInfo)) {
>         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>                        _("a device with the same address already exists "));
>         return -1;
>     }
> 
> to virDomainDefCompatibleDevice and remove the (new)hostdev and
> (existing)rng checks, then I believe it covers the existing cases.

Yes, this looks reasonable.

Michal