Kernel 6.12.x built with qubes-builderv2 cannot boot when used for qubes

[Minimalist73]

Qubes OS release

r4.2.3 (r4.3 too I would guess)

Brief summary

When building one of the 6.12 kernel versions with qubes-builderv2, the kernel won't boot when used for qubes.
libxl immediately displays an error message.
libxl-driver.log contains the following:

xc: panic: xg_dom_bzimageloader.c:761: xc_dom_probe_bzimage_kernel unable to XZ decompress kernel: Invalid kernel
xc: panic: xg_dom_core.c:689: xc_dom_find_loader: no loader found: Invalid kernel
libxl: libxl_dom.c:571:libxl__build_dom: xc_dom_parse_image failed
libxl: libxl_create.c:1716:domcreate_rebuild_done: Domain 58:cannot (re-)build domain: -3

Steps to reproduce

• Build kernel 6.12.x using qubes-builderv2 (UPDATE: 6.12.1 qubes-linux-kernel#1038)
• Move the .rpm files to dom0 and install them
• Start any qube
• Get boot errors

Expected behavior

qubes boot just like any previous kernel version.

Actual behavior

qubes don't boot and shows an error.

[marmarek]

This is already fixed in QubesOS/qubes-vmm-xen@d63e9a9 (R4.3). It will get backported to R4.2 before 6.12 kernel hits R4.2 repos.