APPLIED/Cmnt: [SRU Jammy PATCH 0/1] Change TDP_MMU default for 5.15 kernels

[Stefan Bader]

On 30.08.23 16:45, Stefan Bader wrote:
> Impact:
> We had reports of VM setups which would show intermediate crashes and after
> that locking up completely. This could be reproduced with large memory setups.
> The problem seems to be that fixes to performance regressions caused more
> problems in 5.15 kernels and the full fixes are too intrusive to be backported.
> 
> Fix:
> The following patch was recently sent to the upstream stable mailing list and
> looks to be making its way into linux-5.15.y. This changes the default value
> of kvm.tdp_mmu to off (if anyone is willing to take the risks, this can be
> changed back in config).
> 
> Regression potential:
> VM hosts with many large memory tennants might see a performance impact which
> the TDP MMU approach tried to solve. If those did not see other problems they
> might turn this on again.
> 
> Testcase:
> Large openstack instance (64GB memory, AMD CPU (using SVM)) with a large second
> level guest (32GB memory). Repeatedly starting and stopping the 2nd level guest.
> 
> 

Applied to jammy:linux/master-next (with adjusted BugLink placement and 
provenance). Thanks.

-Stefan
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_0xE8675DEECBEECEA3.asc
Type: application/pgp-keys
Size: 44613 bytes
Desc: OpenPGP public key
URL: <https://lists.ubuntu.com/archives/kernel-team/attachments/20230831/d40ee97d/attachment-0001.key>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_signature
Type: application/pgp-signature
Size: 833 bytes
Desc: OpenPGP digital signature
URL: <https://lists.ubuntu.com/archives/kernel-team/attachments/20230831/d40ee97d/attachment-0001.sig>