Kernel panic

[dollebrekel]

Kernel panic and grub_memalign issue on Z790 + RTX 5090 + 128GB RAM

Hi,

I'm running into a boot issue and would appreciate any guidance.

Hardware:

• ASUS Maximus Z790
• RTX 5090
• 128GB RAM

History:

• Omarchy was working fine for a long time.
• After an Omarchy update the system became increasingly unstable.
• Random freezes started appearing and became more frequent over time.
• Eventually Linux stopped booting.

Errors:

• grub_memalign: Out of memory
• VFS: Unable to mount root fs on unknown-block(0,0)

What I tested:

• Memtest86+ passes successfully.
• Windows boots and runs normally.
• Linux partitions were removed completely.
• Latest Omarchy ISO downloaded again.
• USB recreated using Balena Etcher.
• The same boot problem occurs even from the live USB.

Additional observations:

• EFI partition is readable.
• Limine configuration is present.
• The issue remains even after removing the previous Linux installation.

Questions:

• Has anyone seen similar issues on Z790 systems with RTX 5090 and 128GB RAM?
• Could this be related to Limine, kernel parameters, firmware, BIOS compatibility, or memory mapping?
• Are there any recommended boot parameters or debugging steps?

Thanks in advance.

[dollebrekel]

Update: Resolved

The live USB boot issue turned out to be caused by Resizable BAR (ReBAR) + Above 4G Decoding in the UEFI BIOS, combined with the large memory footprint of 128GB RAM and the RTX 5090's PCIe address space.

With ReBAR enabled, the firmware's memory map becomes highly fragmented, leaving Limine/GRUB with no contiguous memory region to allocate from — hence the grub_memalign: Out of memory error. The VFS: Unable to mount root fs on unknown-block(0,0) was a downstream failure because the kernel never loaded properly in the first place.

Fix:

• Disabled Resizable BAR in UEFI
• Disabled Above 4G Decoding temporarily
• Live USB booted successfully after that

Memtest86+ passed throughout, and Windows was unaffected, which made this tricky to diagnose — both bypass the bootloader memory allocation entirely.

For anyone on Z790 + high VRAM GPU + 128GB+ RAM hitting the same symptoms: toggle ReBAR off first before assuming a hardware or installer issue.

[hhdri]

Same panic on a ROG STRIX Z790-A GAMING WIFI II, BIOS 2001 (2025-04-25). The fix in this thread cannot be completed: Re-Size BAR can be disabled, but Above 4G Decoding is greyed out and stays that way. Disabling ReBAR does not unlock it. ReBAR off plus a rear USB port booted the Omarchy stick once, then grub_memalign:552:out of memory came back. Not deterministic.

EFI-stub/systemd-boot bypass did reach the installer. Details: omacom/omarchy-iso#128