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

[John Ferlan]

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.

Tks -

John