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

[Michal Prívozník]

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 &&

Michal