On 08/16/2016 11:41 AM, Michal Privoznik wrote:
Depending on domain OS type, and interface address type we might not want to use -netdev even though qemu has the capability. We should use more advanced check implemented in qemuDomainSupportsNetdev() function.
So the effect of using qemuDomainSupportsNetdev rather than a direct check of the capability is that aarch64 network devices that are using neither PCI nor virtio-mmio connections would get a different commandline. Is there a particular situation where this makes a difference, or did it just "look like the right thing to do"? I ask this because the more I look at qemuDomainSupportsNetdev() and qemuDomainSupportsNicdev(), the more I wonder if they're still accomplishing what was originally intended (or if what was originally intended is still necessary).
qemuDomainSupportsNicdev() (called by qemuDomainSupportsNetdev()) says that its raison d'etre is
"non-virtio ARM nics require legacy -net nic"
But that's not really what's checked for; instead, it's checking if the
network device has a virtio-mmio *or PCI* address - the result of this
test for both virtio-net-pci and for emulated NICs (do they even work on
aarch64? (e1000 for example - the qemu-system-aarch64 binary says it's
compiled in, but has it actually been tested, or was it just "not taken
out"?)) is the same, so virtio and emulated NICs will both get the
netdev-type commandline.
For that matter, by the time the post-parse is done, any interface device that hasn't had a manually-specified <address> element is going to have either type='pci' or type='virtio-mmio' (is an address type of virtio-mmio a valid thing for a non-virtio emulated device? I wouldn't think so, but I'm just going on common sense, not on any actual knowledge). And as far as I can see, the only network device that can even use any address type other than virtio-mmio or PCI is "usb-net", which requires <address type='usb' .../>.
(I looked back through the git history a bit, and that function was added prior to support for PCI on ARM (when support for virtio-mmio addressing was added - see commits 54a77c and 4fa172), and it looks like it was intended to force the use of -net rather than -netdev when virtio-mmio addressing isn't used. But before virtio-mmio and support for PCI addresses, how were these devices connected in the guest? And now is it even a useful thing at all, or is it obsolete? Cole?
Signed-off-by: Michal Privoznik <mpriv...@redhat.com> --- src/qemu/qemu_hotplug.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c index d1acdd9..feb1f44 100644 --- a/src/qemu/qemu_hotplug.c +++ b/src/qemu/qemu_hotplug.c @@ -1108,7 +1108,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,releaseaddr = true; - if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) {+ if (qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) { vlan = -1; } else { vlan = qemuDomainNetVLAN(net); @@ -1134,7 +1134,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver, goto cleanup; }- if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) {+ if (qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) { if (!(netstr = qemuBuildHostNetStr(net, driver, ',', -1, tapfdName, tapfdSize, @@ -1149,7 +1149,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver, }qemuDomainObjEnterMonitor(driver, vm);- if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) { + if (qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) { if (qemuMonitorAddNetdev(priv->mon, netstr, tapfd, tapfdName, tapfdSize, vhostfd, vhostfdName, vhostfdSize) < 0) { @@ -1195,7 +1195,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver, } else { qemuDomainObjEnterMonitor(driver, vm);- if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) {+ if (qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) { if (qemuMonitorSetLink(priv->mon, net->info.alias, VIR_DOMAIN_NET_INTERFACE_LINK_STATE_DOWN) < 0) { ignore_value(qemuDomainObjExitMonitor(driver, vm)); virDomainAuditNet(vm, NULL, net, "attach", false); @@ -1278,7 +1278,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver, goto cleanup;if (vlan < 0) {- if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) { + if (qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) { char *netdev_name; if (virAsprintf(&netdev_name, "host%s", net->info.alias) < 0) goto cleanup; @@ -3326,7 +3326,7 @@ qemuDomainRemoveNetDevice(virQEMUDriverPtr driver, goto cleanup;qemuDomainObjEnterMonitor(driver, vm);- if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) { + if (qemuDomainSupportsNetdev(vm->def, priv->qemuCaps, net)) { if (qemuMonitorRemoveNetdev(priv->mon, hostnet_name) < 0) { if (qemuDomainObjExitMonitor(driver, vm) < 0) goto cleanup;
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