[PATCH] qemu: Set proper PCI backend for <interface/>-s that are actually hostdevs

[Martin Kletzander]

On Thu, Jun 01, 2023 at 05:25:14PM +0200, Michal Prívozník wrote:
>On 6/1/23 15:26, Michal Privoznik wrote:
>> When starting a domain, it's done so in two steps (actually more,
>> but lets focus on just the following two):
>>
>>   1) qemuProcessPrepareDomain(), followed by
>>
>>   2) qemuProcessPrepareHost().
>>
>> Now, in the first step (PrepareDomain()), PCI backends for all
>> hostdevs is set (qemuProcessPrepareDomain() ->
>> qemuProcessPrepareDomainHostdevs() -> qemuDomainPrepareHostdev()
>> -> qemuDomainPrepareHostdevPCI()). Perfect.
>>
>> But then, additional hostdevs may appear, because in the host
>> prepare phase we may insert some hostdevs into domain definition
>> (qemuProcessPrepareHost() -> qemuProcessNetworkPrepareDevices()).
>>
>> Now, these additional hostdevs don't undergo the same prepare as
>> hostdevs that were already present in the domain definition (i.e.
>> in qemuProcessPrepareDomain() phase). Therefore, we have to call
>> corresponding prepare function explicitly.
>>
>> NB, the interface hotplug code (qemuDomainAttachNetDevice()) does
>> not suffer from this problem, because it calls top level
>> qemuDomainAttachHostDevice() which is used to hotplug regular
>> hostdevs too and as such calls qemuDomainPrepareHostdev().
>>
>> Fixes: 3b87709c768480e085556e06bd8d08f62270d42d
>> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2209853
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>  src/qemu/qemu_process.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index 730e59eb7e..1431fa8310 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>> @@ -5834,6 +5834,13 @@ qemuProcessNetworkPrepareDevices(virQEMUDriver *driver,
>>                                 net->data.network.name, def->name);
>>                  return -1;
>>              }
>> +
>> +            /* For hostdev present in qemuProcessPrepareDomain() phase this was
>> +             * done already, but this code runs after that, so we have to call
>> +             * it ourselves. */
>> +            if (qemuDomainPrepareHostdevPCI(hostdev, priv) < 0)
>
>This should have been just qemuDomainPrepareHostdev() (i.e. without the
>PCI suffix). Forgot to squash it in before sending. Fixed locally.
>
>> +                return -1;
>> +
>>              if (virDomainHostdevInsert(def, hostdev) < 0)
>>                  return -1;
>>          } else if (actualType == VIR_DOMAIN_NET_TYPE_USER &&
>

Sounds reasonable, looks good

Reviewed-by: Martin Kletzander <mkletzan at redhat.com>

>Michal
>
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