Re: [PATCH 1/4] qemu: Generate shorter channel target paths
On Wed, Jul 12, 2023 at 04:49:53PM +0200, Michal Privoznik wrote:
A <channel/> device is basically an UNIX socket into guest.
Whatever is sent from the host, appears in the guest and vice
versa. But because of that, the length of the path to the socket
is important (underscored by fact that we derive the path from
domain short name). But there are still cases where we might not
fit into UNIX_PATH_MAX limit (usually 108 characters), because
the path is derived also from other variables, e.g.
XDG_CONFIG_HOME for session domains.
There is one component though, that's needless: "/target/". Drop
it. This is safe to do, because running domains have their path
saved in status XML and even though paths are dropped on
migration, they are not part of guest ABI and thus we are free to
change them.
This mentions dropping '/target/' which makes sense, but...
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 94587638c3..b4844351ba 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -1780,7 +1780,7 @@ qemuDomainSetPrivatePaths(virQEMUDriver *driver,
priv->libDir = g_strdup_printf("%s/domain-%s", cfg->libDir,
domname);
if (!priv->channelTargetDir)
- priv->channelTargetDir = g_strdup_printf("%s/domain-%s",
+ priv->channelTargetDir = g_strdup_printf("%s/%s",
cfg->channelTargetDir, domname);
...this is also dropping 'domain-' which also makes sense, but
is not mentioned in the commit message.
@@ -5352,9 +5352,12 @@ qemuDomainDefaultNetModel(const virDomainDef
*def,
* libvirt 1.2.19 - 1.3.2:
* {cfg->channelTargetDir}/domain-{dom-name}/{target-name}
*
- * libvirt 1.3.3 and newer:
+ * libvirt 1.3.3 - 9.4.0:
* {cfg->channelTargetDir}/domain-{dom-id}-{short-dom-name}/{target-name}
*
+ * libvirt 9.6.0 and newer:
+ * {cfg->channelTargetDir}/{dom-id}-{short-dom-name}/{target-name}
+ *
This doesn't make it clear that 'cfg->channelTargetDir' is actually
different in those two examples. Should we change th old ones to
libvirt 1.2.19 - 1.3.2:
{cfg->channelTargetDir}/target/domain-{dom-name}/{target-name}
libvirt 1.3.3 - 9.4.0:
{cfg->channelTargetDir}/target/domain-{dom-id}-{short-dom-name}/{target-name}
* The unix socket path was stored in config XML until libvirt
1.3.0.
* If someone specifies the same path as we generate, they shouldn't do it.
*
@@ -5379,7 +5382,7 @@ qemuDomainChrDefDropDefaultPath(virDomainChrDef *chr,
cfg = virQEMUDriverGetConfig(driver);
virBufferEscapeRegex(&buf, "^%s", cfg->channelTargetDir);
- virBufferAddLit(&buf, "/([^/]+\\.)|(domain-[^/]+/)");
+ virBufferAddLit(&buf,
"/(target/)?([^/]+\\.)|(domain-[^/]+/)|([0-9]+-[^/]+/)");
virBufferEscapeRegex(&buf, "%s$", chr->target.name);
diff --git
a/tests/qemuhotplugtestdevices/qemuhotplug-qemu-agent-detach.xml
b/tests/qemuhotplugtestdevices/qemuhotplug-qemu-agent-detach.xml
index 0c3c70a78e..2e5cbfe09c 100644
--- a/tests/qemuhotplugtestdevices/qemuhotplug-qemu-agent-detach.xml
+++ b/tests/qemuhotplugtestdevices/qemuhotplug-qemu-agent-detach.xml
@@ -1,5 +1,5 @@
<channel type='unix'>
- <source mode='bind'
path='/var/lib/libvirt/qemu/channel/target/domain-7-hotplug/org.qemu.guest_agent.0'/>
+ <source mode='bind'
path='/var/lib/libvirt/qemu/channel/target/7-hotplug/org.qemu.guest_agent.0'/>
You dropped 'domain-' but didn't drop '/target'. Same in a few other
cases below
With regards,
Daniel
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