Hi Tim,
you are right that neither of the workaround steps were necessary on 22.04 and
they should neither be on 24.04.
### Topic 1 - changes that should not be needed
Ubuntu 24.04 by default has
1. hugetlbfs mounted (was that no more the case for you after upgrade?)
$ mount | grep huge
hugetlbfs on /dev/hugepages type hugetlbfs
(rw,nosuid,nodev,relatime,pagesize=2M)
2. uncommenting hugetlbfs_mount in /etc/libvirt/qemu.conf changes nothing
default is
#hugetlbfs_mount = "/dev/hugepages"
Changing that to
hugetlbfs_mount = "/dev/hugepages"
will not change anything.
I assume #1 and #2 have only been things on your try to debug what is wrong -
which is fine.
But let us know if it is otherwise.
### Topic 2 - was there an apparmor denial?
Now back to your actual issue, you mentioned that you set apparmor to complain
mode.
Was there an indication that apparmor is the issue, a related denial in the
syslog when you start your guest? If so could you please pass that denial?
### Topic 3 - repro seems to not trigger this
I picked a guest which before had:
<memory unit='MiB'>1024</memory>
<currentMemory unit='MiB'>1024</currentMemory>
And changed it to use huge pages by adding:
<memoryBacking>
<hugepages>
<page size='2048' unit='KiB'/>
</hugepages>
</memoryBacking>
To confirm it tries to use the right thing I started it without allocating huge
pages and got:
=> qemu-system-x86_64: unable to map backing store for guest RAM: Cannot
allocate memory
Then I allocated some huge pages in the system and started it again.
$ echo 512 | sudo tee -a /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
$ virsh start --console test
Worked right away.
I double checked in /proc/meminfo and saw HugePages_Free changing when the
guest was running.
So I think, something is configured in an unexpected way.
Could you share
- your full guest-config in regard to memory
- hugeadm --list-all-mounts
- journalctl -f while starting the guest
- grep -i huge /proc/meminfo
** Changed in: libvirt (Ubuntu)
Status: New => Incomplete
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https://bugs.launchpad.net/bugs/2073214
Title:
hugepages causes permissions error
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