RHCOS 4.12.3 and 4.12.10 on Z display the "swiotlb buffer is full" message during KVM cluster Secure Execution (SE) install boots for the bootstrap, master, worker nodes, elongating boot durations

1. When installing an OCP 4.12.10 and 4.12.11 on Z KVM Secure Execution (SE) mode cluster with RHCOS 4.12.3 or 4.12.10 on Z, during the ignition boot process of the bootstrap, master, and worker nodes the console displays the "swiotlb buffer is full" message.

2. As an example:
[   31.655847] xor: automatically using best checksumming function   xc
[    **] A start job is running for Ignition (disks) (39s / no limit)[   42.220115] Key type encrypted registered
[   ***] A start job is running for Ignition (disks) (40s / no limit)[   42.306911] alg: No test for authenc(hmac(sha256),xts(aes)) (authenc(hmac(sha256-s390),xts-aes-s390))
[   44.116873] ignition[1189]: disks: createLuks: op(7): [finished] creating "boot"
[   44.117073] ignition[1189]: disks: createLuks: op(8): [started]  opening luks device boot
[   46.263908] ignition[1189]: disks: createLuks: op(8): [finished] opening luks device boot
[   46.263985] ignition[1189]: disks: createLuks: op(9): [started]  wiping filesystem signatures from "/run/ignition/dev_aliases/dev/disk/by-partlabel/root"
[   46.275722] ignition[1189]: disks: createLuks: op(9): [finished] wiping filesystem signatures from "/run/ignition/dev_aliases/dev/disk/by-partlabel/root"
[   46.275794] ignition[1189]: disks: createLuks: op(a): [started]  creating "root"
[   51.127538] virtio_ccw 0.0.0000: swiotlb buffer is full (sz: 262144 bytes), total 32768 (slots), used 28764 (slots)
[   51.127690] virtio_ccw 0.0.0000: swiotlb buffer is full (sz: 262144 bytes), total 32768 (slots), used 28764 (slots)
[   51.134643] virtio_ccw 0.0.0000: swiotlb buffer is full (sz: 262144 bytes), total 32768 (slots), used 28249 (slots)
[    **] A start job is running for Ignition (disks) (59s / no limit)


3. The "swiotlb buffer is full" condition seems to negatively impact the speed of the boot of the OCP on Z bootstrap, master, and worker nodes, requiring retries during the ignition process, resulting in elongated times to boot, compared to non-Secure Execution install mode boots of these OCP on Z nodes where this does not seem to be an issue.

4. The current swiotlb buffer size is 262144 bytes, total 32768 slots.

5. Should the RHCOS 4.12.3 and 4.12.10 on Z (and the corresponding RHCOS 4.13 on Z) builds' default swiotlb buffer size be increased to avoid this full condition and presumably enable the Secure Execution mode ignition boot process to be more efficient?  


Thank you.

RHCOS 4.12.3 and 4.12.10 on Z

1. Consistently reproducible.

1. Attempt to install a KVM OCP 4.12.10 or 4.12.11 on Z using RHCOS 4.12.3 or 4.12.10 on Z cluster in Secure Execution (SE) mode. 

1. The bootstrap, master, and worker nodes display the "swiotlb buffer is full" message, with the ignition boot process requiring apparent retries and as a result, additional time to complete, with the worker node ignition process even failing a subset of the times attempted.

1. The bootstrap, master, and worker nodes should not display the "swiotlb buffer is full" message, and continue the ignition process without apparent retries.