On 2/12/19 11:19 PM, John Ferlan wrote:
On 2/11/19 10:40 AM, Michal Privoznik wrote:
>
https://bugzilla.redhat.com/show_bug.cgi?id=1624204
>
> The guestfwd channels are -netdevs really. Hotunplug them as
> such. Also, DEVICE_DELETED event is not triggered (surprisingly,
> since we're not issuing device_del rather than netdev_del) and
> associated chardev is removed automagically too. This means that
> we need to do qemuDomainRemoveChrDevice() minus monitor call to
> remove the chardev.
>
> Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
> ---
> src/qemu/qemu_hotplug.c | 48 ++++++++++++++++++++++++++++-------------
> 1 file changed, 33 insertions(+), 15 deletions(-)
>
So while, yes this does work and fix the issue... It's still not going
to be able to remove any guestfwd that is already assigned to a guest
because it'll have that "user-" prefix... It will work once the guest
is restarted of course... so...
> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index a0ccc3b82c..107d0fb7a9 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c
> @@ -4742,25 +4742,28 @@ qemuDomainRemoveNetDevice(virQEMUDriverPtr driver,
> static int
> qemuDomainRemoveChrDevice(virQEMUDriverPtr driver,
> virDomainObjPtr vm,
> - virDomainChrDefPtr chr)
> + virDomainChrDefPtr chr,
> + bool monitor)
> {
> virObjectEventPtr event;
> char *charAlias = NULL;
> qemuDomainObjPrivatePtr priv = vm->privateData;
> int ret = -1;
> - int rc;
> + int rc = 0;
>
> VIR_DEBUG("Removing character device %s from domain %p %s",
> chr->info.alias, vm, vm->def->name);
>
> - if (!(charAlias = qemuAliasChardevFromDevAlias(chr->info.alias)))
> - goto cleanup;
> + if (monitor) {
> + if (!(charAlias = qemuAliasChardevFromDevAlias(chr->info.alias)))
> + goto cleanup;
>
> - qemuDomainObjEnterMonitor(driver, vm);
> - rc = qemuMonitorDetachCharDev(priv->mon, charAlias);
> + qemuDomainObjEnterMonitor(driver, vm);
> + rc = qemuMonitorDetachCharDev(priv->mon, charAlias);
>
> - if (qemuDomainObjExitMonitor(driver, vm) < 0)
> - goto cleanup;
> + if (qemuDomainObjExitMonitor(driver, vm) < 0)
> + goto cleanup;
> + }
>
> if (rc == 0 &&
> qemuDomainDelChardevTLSObjects(driver, vm, chr->source, charAlias) <
0)
> @@ -5064,7 +5067,7 @@ qemuDomainRemoveDevice(virQEMUDriverPtr driver,
> break;
>
> case VIR_DOMAIN_DEVICE_CHR:
> - ret = qemuDomainRemoveChrDevice(driver, vm, dev->data.chr);
> + ret = qemuDomainRemoveChrDevice(driver, vm, dev->data.chr, true);
> break;
> case VIR_DOMAIN_DEVICE_RNG:
> ret = qemuDomainRemoveRNGDevice(driver, vm, dev->data.rng);
> @@ -6127,6 +6130,7 @@ int qemuDomainDetachChrDevice(virQEMUDriverPtr driver,
> virDomainDefPtr vmdef = vm->def;
> virDomainChrDefPtr tmpChr;
> char *devstr = NULL;
> + bool guestfwd = false;
>
> if (!(tmpChr = virDomainChrFind(vmdef, chr))) {
> virReportError(VIR_ERR_DEVICE_MISSING,
> @@ -6136,6 +6140,11 @@ int qemuDomainDetachChrDevice(virQEMUDriverPtr driver,
> goto cleanup;
> }
>
> + /* guestfwd channels are not really -device rather than
> + * -netdev. We need to treat them slightly differently. */
> + guestfwd = tmpChr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CHANNEL
&&
> + tmpChr->targetType ==
VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_GUESTFWD;
> +
> if (!tmpChr->info.alias && qemuAssignDeviceChrAlias(vmdef, tmpChr,
-1) < 0)
> goto cleanup;
>
> @@ -6144,22 +6153,31 @@ int qemuDomainDetachChrDevice(virQEMUDriverPtr driver,
> if (qemuBuildChrDeviceStr(&devstr, vmdef, tmpChr, priv->qemuCaps) <
0)
> goto cleanup;
Bright idea...
The returned @devstr contains the "id=" value used to generate the
command line, thus why not extract out the id= value to be the alias
used below for either qemuMonitorRemoveNetdev or qemuMonitorDelDevice?
Problem with this approach is that string processing in C is pain in the
#@$. Cutting out the alias from @devstr would be not trivial. But okay,
there's another approach - have yet another local variable that would be
initialized to tmpChr->info.alias and then qemuBuildChrDeviceStr() might
override it for those types of chardev that need it. But this is rather
ugly.
That way patch2 becomes unnecessary (I tried it). Of course fear always
strikes my soul when "assuming" anything, so I figured I'd run it past
you first for your thoughts. I am OK with the patches as they are
except for the tiny gotcha of never being able to remove that
user-channel# device.
Well, one way to look at it might be: if you have a domain started via
older libvirt nothing changes for you. You're unable to detach guestfwd
just like you always was :-)
Then again, guestfwd really makes sense only with slirp (that's also why
qemu rejects any other IP than 10.0.2.1) and since we're not setting
other attributes for the netdev, the defaults are used. I mean,
-netdev user,net=172.17.2.0/24,ipv6-net=2001:db8:ac10:fd01::/64,\
guestfwd=tcp:172.17.2.4:4600-chardev:charchannel1,id=channel1
is the way to set different address for guestfwd. But so far, we are not
setting net= nor ipv6-net= for guestfwd <channel/> (although, we are
doing that for <interface type='user'/>). Therefore I think, no one is
using guestfwd really. That's why I am willing to take the risk.
Having said that, I'm not sure how to fix the lack of attributes
described above and thus allowing users to specify a different address.
I mean, we can extend <channel/> for new attributes and just put them on
the cmd line, but then it is effectively not a channel but an
<interface/> (more specifically <interface type='user/> which shows up
even in guest.
Or we could try to pair guestfwd channels with <interface type='user'/>
but the question is using what key? The Nth guestfwd would correspond do
Nth <interface type='user'/>? This link would not be apparent from
domain XML. Looks like we're doomed here.
>
> - if (!async)
> + if (!async && !guestfwd)
> qemuDomainMarkDeviceForRemoval(vm, &tmpChr->info);
>
> qemuDomainObjEnterMonitor(driver, vm);
> - if (devstr && qemuMonitorDelDevice(priv->mon, tmpChr->info.alias)
< 0) {
> - ignore_value(qemuDomainObjExitMonitor(driver, vm));
> - goto cleanup;
Hmm... If one considers that if @devstr were NULL, then this code would
do nothing, then what is it's purpose? There is no other consumer of
qemuBuildChrDeviceStr that could believe @devstr == NULL and ret == 0
that I could find.
Looks like an old artefact. And looking at the commit 24b0821926e that
introduced it (oh boy, I was so young once) and indeed it is. Back in
2013 when there was no DEVICE_DELETED event libvirt detached both front-
and backend at the same time. Well, this check in question was there to
remove frontend only for those chardevs that had one.
Michal