Comment 25 for bug 468413

I can confirm this bug too. Using 10.04 LTS Lucid Lynx RC (LiveCD only atm). Can't boot with KMS enabled. At some point, boot process hangs repeatedly showing message "BUG: soft lockup - CPU #0 stuck for 61s! [plymouthd:1183]" every minute or so. Somehow I were able to boot into command prompt and after looking trough logs, I saw error messages involving AGP GART and agpgart-amd64 loading after DRM initialization just as described in bug description here. I can boot successfully if I enable "nomodeset" boot option but splash (plymouth) is shown in low res and low color mode and DRI (including 3D acceleration) is not working.

Fedora 13 Beta works correctly but judging by lsmod an dmesg, Fedora seems to have agpgart-amd64 module built into the kernel. It loads before DRM initialization as expected.

Computer:
ASUS K8N (nforce3) motherboard
Athlon64 3200+
Radeon 9250 (RV280), 256MB