[libvirt] [PATCHv3 10/11] qemu: Adapt qemuBuildInterfaceCommandLine to to multiqueue net

[Michal Privoznik]

On 20.05.2013 19:15, Laine Stump wrote:
> On 05/16/2013 08:49 AM, Michal Privoznik wrote:
>> ---
>>  src/qemu/qemu_command.c | 82 ++++++++++++++++++++++++++++++++++---------------
>>  1 file changed, 58 insertions(+), 24 deletions(-)
>>

>>              goto cleanup;
>>      } else if (actualType == VIR_DOMAIN_NET_TYPE_DIRECT) {
>> -        tapfd = qemuPhysIfaceConnect(def, driver, net, qemuCaps, vmop);
>> -        if (tapfd < 0)
>> +        if (VIR_ALLOC(tapfd) < 0 || VIR_ALLOC(tapfdName) < 0) {
>> +            virReportOOMError();
>> +            goto cleanup;
>> +        }
>> +        tapfdSize = 1;
>> +        tapfd[0] = qemuPhysIfaceConnect(def, driver, net,
>> +                                        qemuCaps, vmop);
> 
> 
> macvtap doesn't support multiple queues? But macvtap is supposed to be
> the panacea of high performance...

Unfortunately not yet. Macvtap is still under development in question of MQ.

> 
> 
> 
>> +        if (tapfd[0] < 0)
>>              goto cleanup;
>>      }
>>  
>> @@ -6510,28 +6526,34 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
>>          actualType == VIR_DOMAIN_NET_TYPE_DIRECT) {
>>          /* Attempt to use vhost-net mode for these types of
>>             network device */
>> -        int vhostfd;
>> -        int vhostfdSize = 1;
>> +        if (VIR_ALLOC(vhostfd) < 0 || VIR_ALLOC(vhostfdName)) {
>> +            virReportOOMError();
>> +            goto cleanup;
>> +        }
>> +        vhostfdSize = 1;
> 
> 
> I am *really* losing track of which layer of which set of fds is getting
> the "multi" treatment in each patch. I think there are just too many
> steps in this patch series. It would be easier to follow if there was a
> patch to add the config parser/formatter/rng/docs, then just another
> single patch to wire that data all the way up and down the stack. I find
> myself spending time at each stage ttrying to decide if something is a
> bug, or just an interim thing that will be fixed in a later step.
> 

Well, I keep modifying patches as you review them. I think I gonna post
one more version - just in the form as you requested.

> 
> 
>> +
>> +        if (qemuOpenVhostNet(def, net, qemuCaps, vhostfd, &vhostfdSize) < 0)
>> +            goto cleanup;
>> +    }
>>  
>> -        if (qemuOpenVhostNet(def, net, qemuCaps, &vhostfd, &vhostfdSize) < 0)
>> +    for (i = 0; i < tapfdSize; i++) {
>> +        virCommandTransferFD(cmd, tapfd[i]);
>> +        if (virAsprintf(&tapfdName[i], "%d", tapfd[i]) < 0) {
>> +            virReportOOMError();
>>              goto cleanup;
>> -        if (vhostfdSize > 0) {
>> -            virCommandTransferFD(cmd, vhostfd);
>> -            if (virAsprintf(&vhostfdName, "%d", vhostfd) < 0) {
>> +        }
>> +    }
>> +
>> +    for (i = 0; i < vhostfdSize; i++) {
>> +        if (vhostfd[i] >= 0) {
>> +            virCommandTransferFD(cmd, vhostfd[i]);
>> +            if (virAsprintf(&vhostfdName[i], "%d", vhostfd[i]) < 0) {
>>                  virReportOOMError();
>>                  goto cleanup;
>>              }
>>          }
>>      }
>>  
>> -    if (tapfd >= 0) {
>> -        virCommandTransferFD(cmd, tapfd);
>> -        if (virAsprintf(&tapfdName, "%d", tapfd) < 0) {
>> -            virReportOOMError();
>> -            goto cleanup;
>> -        }
>> -    }
>> -
>>      /* Possible combinations:
>>       *
>>       *  1. Old way:   -net nic,model=e1000,vlan=1 -net tap,vlan=1
>> @@ -6544,8 +6566,8 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
>>          virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) {
>>          if (!(host = qemuBuildHostNetStr(net, driver,
>>                                           ',', vlan,
>> -                                         &tapfdName, tapfdName ? 1 : 0,
>> -                                         &vhostfdName, vhostfdName ?  1 : 0)))
>> +                                         tapfdName, tapfdSize,
>> +                                         vhostfdName, vhostfdSize)))
>>              goto cleanup;
>>          virCommandAddArgList(cmd, "-netdev", host, NULL);
>>      }
>> @@ -6562,8 +6584,8 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
>>            virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE))) {
>>          if (!(host = qemuBuildHostNetStr(net, driver,
>>                                           ',', vlan,
>> -                                         &tapfdName, tapfdName ? 1 : 0,
>> -                                         &vhostfdName, vhostfdName ? 1 : 0)))
>> +                                         tapfdName, tapfdSize,
>> +                                         vhostfdName, vhostfdSize)))
>>              goto cleanup;
>>          virCommandAddArgList(cmd, "-net", host, NULL);
>>      }
>> @@ -6572,6 +6594,18 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
>>  cleanup:
>>      if (ret < 0)
>>          virDomainConfNWFilterTeardown(net);
>> +    for (i = 0; i < tapfdSize; i++) {
>> +        if (ret < 0)
>> +            VIR_FORCE_CLOSE(tapfd[i]);
>> +        VIR_FREE(tapfdName[i]);
> 
> 
> Okay, tapfdSize isn't set until/unless tapfd and tapfdName are both
> successfully allocated...
> 
> 
>> +    }
>> +    for (i = 0; i < vhostfdSize; i++) {
>> +        if (ret < 0)
>> +            VIR_FORCE_CLOSE(vhostfd[i]);
>> +        VIR_FREE(vhostfdName[i]);
> 
> 
> Same here. (I mention this because I was worried about it initially :-)
> 
> 
>> +    }
>> +    VIR_FREE(tapfd);
>> +    VIR_FREE(vhostfd);
>>      VIR_FREE(nic);
>>      VIR_FREE(host);
>>      VIR_FREE(tapfdName);
> 
> ACK, aside from making tapfdSize an int* (so it can be modified on
> failure/non-support in qemuIfaceNetworkConnect), and an answer about
> support for multiple queues when macvtap is used.
> 
> Oh, actually another problem - in cases where multiple queues are
> requested and can't be honored due to interface type (or any other
> reason), I think we should log an error and fail, but it looks like you
> just ignore it. So I guess that also needs fixing (or an explanation).

Yeah, I was thinking about it too.

Michal