libvirt/docs/kbase
Michal Privoznik 0377177c78 qemu_process.c: Propagate hugetlbfs mounts on reconnect
When reconnecting to a running QEMU process, we construct the
per-domain path in all hugetlbfs mounts. This is a relict from
the past (v3.4.0-100-g5b24d25062) where we switched to a
per-domain path and we want to create those paths when libvirtd
restarts on upgrade.

And with namespaces enabled there is one corner case where the
path is not created. In fact an error is reported and the
reconnect fails. Ideally, all mount events are propagated into
the QEMU's namespace. And they probably are, except when the
target path does not exist inside the namespace. Now, it's pretty
common for users to mount hugetlbfs under /dev (e.g.
/dev/hugepages), but if domain is started without hugepages (or
more specifically - private hugetlbfs path wasn't created on
domain startup), then the reconnect code tries to create it.
But it fails to do so, well, it fails to set seclabels on the
path because, because the path does not exist in the private
namespace. And it doesn't exist because we specifically create
only a subset of all possible /dev nodes. Therefore, the mount
event, whilst propagated, is not successful and hence the
filesystem is not mounted. We have to do it ourselves.

If hugetlbfs is mount anywhere else there's no problem and this
is effectively a dead code.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2123196
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2022-09-23 16:33:48 +02:00
..
internals qemu & conf: move BeginAsyncJob & EndAsyncJob into src/conf 2022-09-07 12:15:06 +02:00
backing_chains.rst
debuglogs.rst kbase: debuglogs: Add a note about auto-shutdown of daemons 2022-07-07 14:35:30 +02:00
domainstatecapture.rst
index.rst docs: Add kbase page for Secure Boot 2022-07-01 15:10:43 +02:00
kvm-realtime.rst
launch_security_sev.rst
live_full_disk_backup.rst
locking-lockd.rst
locking-sanlock.rst
locking.rst
memorydevices.rst
merging_disk_image_chains.rst
meson.build docs: Add kbase page for Secure Boot 2022-07-01 15:10:43 +02:00
qemu-core-dump.rst
qemu-passthrough-security.rst qemu_process.c: Propagate hugetlbfs mounts on reconnect 2022-09-23 16:33:48 +02:00
rpm-deployment.rst spec: Drop libvirt-daemon-driver-storage-sheepdog package 2022-09-01 13:11:09 +02:00
s390_protected_virt.rst
secureboot.rst kbase: Document how to disable Secure Boot entirely 2022-08-04 14:39:18 +02:00
secureusage.rst
snapshots.rst
systemtap.rst
tlscerts.rst
virtiofs.rst