Description of problem: We have an Intel SR6850HW4 box with 4 dual-core, ht-enabled CPUs on test. After upping NR_CPUS to 16 (see bugzilla 177445) to be able to use all 16 logical CPUs, we got the panic from "arch/x86_64/kernel/io_apic.c": panic("IOAPIC[%d]: Unable change apic_id!\n", ioapic); Googling around shows that this problem seem to be known and fixed in mainline. Solution seem to be to remove the call to "io_apic_get_unique_id" in "mpparse.c" --- linux-2.6.9/arch/x86_64/kernel/mpparse.c-orig 2006-01-09 18:25:18.000000000 +0100 +++ linux-2.6.9/arch/x86_64/kernel/mpparse.c 2006-01-09 18:05:26.000000000 +0100 @@ -763,7 +763,8 @@ mp_ioapics[idx].mpc_apicaddr = address; set_fixmap_nocache(FIX_IO_APIC_BASE_0 + idx, address); - mp_ioapics[idx].mpc_apicid = io_apic_get_unique_id(idx, id); +// mp_ioapics[idx].mpc_apicid = io_apic_get_unique_id(idx, id); + mp_ioapics[idx].mpc_apicid = id; mp_ioapics[idx].mpc_apicver = io_apic_get_version(idx); /* After this the box boots fine and works like expected with 16 CPUs showing. In mainline the fix is slightly bigger, as the routine "io_apic_get_unique_id" is removed alltogether from the tree. Please consider fixing this for official RHEL4 kernels. Version-Release number of selected component (if applicable): Linux muvpl404 2.6.9-22.EL.smp #1 SMP Mon Jan 9 18:33:30 CET 2006 x86_64 x86_64 x86_64 GNU/Linux How reproducible: 100% on decribed hardware Steps to Reproduce: 1. Rebuild kernel with NR_CPUS=16 2. Install on descibed hardware 3. Reboot with "earlyprintk=vga" -> Panic Actual results: Panic Expected results: Boot Additional info: [root@muvpl404 SOURCES]# lspci 00:00.0 Host bridge: Intel Corporation E8500 Hub Interface 1.5 (rev 10) 00:01.0 PCI bridge: Intel Corporation E8500 PCI Express x4 Port D (rev 10) 00:02.0 PCI bridge: Intel Corporation E8500 PCI Express x8 Port C (rev 10) 00:03.0 PCI bridge: Intel Corporation E8500 PCI Express x4 Port C1 (rev 10) 00:04.0 PCI bridge: Intel Corporation E8500 PCI Express x4 Port B0 (rev 10) 00:05.0 PCI bridge: Intel Corporation E8500 PCI Express x4 Port B1 (rev 10) 00:06.0 PCI bridge: Intel Corporation E8500 PCI Express x4 Port A0 (rev 10) 00:07.0 PCI bridge: Intel Corporation E8500 PCI Express x4 Port A1 (rev 10) 00:08.0 Host bridge: Intel Corporation E8500 IMI Registers (rev 10) 00:09.0 RAM memory: Intel Corporation E8500 eXternal Memory Bridge (rev 10) 00:09.1 RAM memory: Intel Corporation E8500 XMB Miscellaneous Registers (rev 10) 00:09.2 RAM memory: Intel Corporation E8500 XMB Memory Interleaving Registers (rev 10) 00:09.3 RAM memory: Intel Corporation E8500 XMB DDR Initialization and Calibration (rev 10) 00:09.4 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:09.5 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:09.6 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:09.7 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0a.0 Host bridge: Intel Corporation E8500 IMI Registers (rev 10) 00:0b.0 RAM memory: Intel Corporation E8500 eXternal Memory Bridge (rev 10) 00:0b.1 RAM memory: Intel Corporation E8500 XMB Miscellaneous Registers (rev 10) 00:0b.2 RAM memory: Intel Corporation E8500 XMB Memory Interleaving Registers (rev 10) 00:0b.3 RAM memory: Intel Corporation E8500 XMB DDR Initialization and Calibration (rev 10) 00:0b.4 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0b.5 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0b.6 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0b.7 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0c.0 Host bridge: Intel Corporation E8500 IMI Registers (rev 10) 00:0d.0 RAM memory: Intel Corporation E8500 eXternal Memory Bridge (rev 10) 00:0d.1 RAM memory: Intel Corporation E8500 XMB Miscellaneous Registers (rev 10) 00:0d.2 RAM memory: Intel Corporation E8500 XMB Memory Interleaving Registers (rev 10) 00:0d.3 RAM memory: Intel Corporation E8500 XMB DDR Initialization and Calibration (rev 10) 00:0d.4 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0d.5 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0d.6 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0d.7 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0e.0 Host bridge: Intel Corporation E8500 IMI Registers (rev 10) 00:0f.0 RAM memory: Intel Corporation E8500 eXternal Memory Bridge (rev 10) 00:0f.1 RAM memory: Intel Corporation E8500 XMB Miscellaneous Registers (rev 10) 00:0f.2 RAM memory: Intel Corporation E8500 XMB Memory Interleaving Registers (rev 10) 00:0f.3 RAM memory: Intel Corporation E8500 XMB DDR Initialization and Calibration (rev 10) 00:0f.4 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0f.5 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0f.6 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:0f.7 RAM memory: Intel Corporation E8500 XMB Reserved Registers (rev 10) 00:10.0 Host bridge: Intel Corporation E8500 Front Side Bus, Boot, and Interrupt Registers (rev 10) 00:10.1 Host bridge: Intel Corporation E8500 Address Mapping Registers (rev 10) 00:10.2 Host bridge: Intel Corporation E8500 RAS Registers (rev 10) 00:11.0 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:11.1 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:11.2 Host bridge: Intel Corporation E8500 Miscellaneous Registers (rev 10) 00:13.0 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.1 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.2 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.3 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.4 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.5 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.6 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:13.7 Host bridge: Intel Corporation E8500 Reserved Registers (rev 10) 00:1d.0 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #1 (rev 02) 00:1d.1 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #2 (rev 02) 00:1d.2 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #3 (rev 02) 00:1d.7 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 EHCI Controller (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev c2) 00:1f.0 ISA bridge: Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface Bridge (rev 02) 00:1f.2 IDE interface: Intel Corporation 82801EB (ICH5) SATA Controller (rev 02) 00:1f.3 SMBus: Intel Corporation 82801EB/ER (ICH5/ICH5R) SMBus Controller (rev 02) 0a:00.0 PCI bridge: Intel Corporation 6700PXH PCI Express-to-PCI Bridge A (rev 09) 0a:00.2 PCI bridge: Intel Corporation 6700PXH PCI Express-to-PCI Bridge B (rev 09) 0c:02.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet (rev 10) 0c:02.1 Ethernet controller: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet (rev 10) 0e:00.0 PCI bridge: Intel Corporation 80332 [Dobson] I/O processor (A-Segment Bridge) (rev 07) 0e:00.2 PCI bridge: Intel Corporation 80332 [Dobson] I/O processor (B-Segment Bridge) (rev 07) 0f:05.0 SCSI storage controller: LSI Logic / Symbios Logic 53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI (rev 08) 0f:05.1 SCSI storage controller: LSI Logic / Symbios Logic 53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI (rev 08) 11:00.0 VGA compatible controller: ATI Technologies Inc Radeon RV100 QY [Radeon 7000/VE]
Just to add more info. Here is the related discussion on the x86_64 list: http://www.x86-64.org/lists/discuss/msg06590.html Cheers Martin
*** This bug has been marked as a duplicate of 168604 ***
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2006-0132.html