The patch from commit e5731f4 ("backport fix for managing block flush
queue list") caused some fallout when used with LVM on root, as that
uses some rather odd (but previously working fine) PREFLUSH
| POSTFLUSH format that was now causing the list to be used without
being initialized, resulting in freezes.
Link: https://lore.kernel.org/all/20240608143115.972486-1-chengming.zhou@linux.dev/
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Reported in the community forum [0] and easy to reproduce by doing
e.g.
> while true; do mount -t nfs 192.168.20.148:/rpool/data /mnt/test; done
from another node for a share that does not exist or for which the
client has no permissions.
[0]: https://forum.proxmox.com/threads/146649
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
The original fix disabled the xsaves feature for zen1/2. The issue has
since been fixed in the cpus microcode and this patch keeps the feature enabled
if the microcode version is recent enough to contain the fix.
Signed-off-by: Folke Gleumes <f.gleumes@proxmox.com>
With apparmor 4, when recvmsg() calls are checked by the apparmor LSM
they will always return EINVAL.
This causes very weird issues when apparmor profiles are in use, and a
lot of networking issues in containers (which are always using
apparmor).
When coming from sys_recvmsg, msg->msg_namelen is explicitly set to
zero early on. (see ____sys_recvmsg in net/socket.c)
We still end up in 'map_addr' where the assumption is that addr !=
NULL means addrlen has a valid size.
This is likely not a final fix, it was suggested by jjohansen on irc
to get things going until this is resolved properly.
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
This reverts commit 29cb6fcbb7, user
feedback was showing any positive impact of this patch, and upstream
still hasn't a fix for older stable releases (but for 6.8), so for now
rather revert this and wait for either a better (well, actual) fix or
updating to 6.8 or newer.
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Users have been reporting [1] that VMs occasionally become
unresponsive with high CPU usage for some time (varying between ~1 and
more than 60 seconds). After that time, the guests come back and
continue running. Windows VMs seem most affected (not responding to
pings during the hang, RDP sessions time out), but we also got reports
about Linux VMs (reporting soft lockups). The issue was not present on
host kernel 5.15 and was first reported with kernel 6.2. Users
reported that the issue becomes easier to trigger the more memory is
assigned to the guests. Setting mitigations=off was reported to
alleviate (but not eliminate) the issue. For most users the issue
seems to disappear after (also) disabling KSM [2], but some users
reported freezes even with KSM disabled [3].
It turned out the reports concerned NUMA hosts only, and that the
freezes correlated with runs of the NUMA balancer [4]. Users reported
that disabling the NUMA balancer resolves the issue (even with KSM
enabled).
We put together a Linux VM reproducer, ran a git-bisect on the kernel
to find the commit introducing the issue and asked upstream for help
[5]. As it turned out, an upstream bugreport was recently opened [6]
and a preliminary fix to the KVM TDP MMU was proposed [7]. With that
patch [7] on top of kernel 6.7, the reproducer does not trigger
freezes anymore. As of now, the patch (or its v2 [8]) is not yet
merged in the mainline kernel, and backporting it may be difficult due
to dependencies on other KVM changes [9].
However, the bugreport [6] also prompted an upstream developer to
propose a patch to the kernel scheduler logic that decides whether a
contended spinlock/rwlock should be dropped [10]. Without the patch,
PREEMPT_DYNAMIC kernels (such as ours) would always drop contended
locks. With the patch, the kernel only drops contended locks if the
kernel is currently set to preempt=full. As noted in the commit
message [10], this can (counter-intuitively) improve KVM performance.
Our kernel defaults to preempt=voluntary (according to
/sys/kernel/debug/sched/preempt), so with the patch it does not drop
contended locks anymore, and the reproducer does not trigger freezes
anymore. Hence, backport [10] to our kernel.
[1] https://forum.proxmox.com/threads/130727/
[2] https://forum.proxmox.com/threads/130727/page-4#post-575886
[3] https://forum.proxmox.com/threads/130727/page-8#post-617587
[4] https://www.kernel.org/doc/html/latest/admin-guide/sysctl/kernel.html#numa-balancing
[5] https://lore.kernel.org/kvm/832697b9-3652-422d-a019-8c0574a188ac@proxmox.com/
[6] https://bugzilla.kernel.org/show_bug.cgi?id=218259
[7] https://lore.kernel.org/all/20230825020733.2849862-1-seanjc@google.com/
[8] https://lore.kernel.org/all/20240110012045.505046-1-seanjc@google.com/
[9] https://lore.kernel.org/kvm/Zaa654hwFKba_7pf@google.com/
[10] https://lore.kernel.org/all/20240110214723.695930-1-seanjc@google.com/
Signed-off-by: Friedrich Weber <f.weber@proxmox.com>
