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Mikael Pettersson 12c247a671 x86: fix boot failure on 486 due to TSC breakage 
> Diffing dmesg between git7 and git8 doesn't sched any light since
 > git8 also removed the printouts of the x86 caps as they were being
 > initialised and updated. I'm currently adding those printouts back
 > in the hope of seeing where and when the caps get broken.

That turned out to be very illuminating:

 --- dmesg-2.6.24-git7	2008-02-24 18:01:25.295851000 +0100
 +++ dmesg-2.6.24-git8	2008-02-24 18:01:25.530358000 +0100
 ...
 CPU: After generic identify, caps: 00000003 00000000 00000000 00000000 00000000 00000000 00000000 00000000

 CPU: After all inits, caps: 00000003 00000000 00000000 00000000 00000000 00000000 00000000 00000000
+CPU: After applying cleared_cpu_caps, caps: 00000013 00000000 00000000 00000000 00000000 00000000 00000000 00000000

Notice how the TSC cap bit goes from Off to On.

(The first two lines are printout loops from -git7 forward-ported
to -git8, the third line is the same printout loop added just after
the xor-with-cleared_cpu_caps[] loop.)

Here's how the breakage occurs:
1. arch/x86/kernel/tsc_32.c:tsc_init() sees !cpu_has_tsc,
   so bails and calls setup_clear_cpu_cap(X86_FEATURE_TSC).
2. include/asm-x86/cpufeature.h:setup_clear_cpu_cap(bit) clears
   the bit in boot_cpu_data and sets it in cleared_cpu_caps
3. arch/x86/kernel/cpu/common.c:identify_cpu() XORs all caps
   in with cleared_cpu_caps
   HOWEVER, at this point c->x86_capability correctly has TSC
   Off, cleared_cpu_caps has TSC On, so the XOR incorrectly
   sets TSC to On in c->x86_capability, with disastrous results.

The real bug is that clearing bits with XOR only works if the
bits are known to be 1 prior to the XOR, and that's not true here.

A simple fix is to convert the XOR to AND-NOT instead. The following
patch does that, and allows my 486 to boot 2.6.25-rc kernels again.

[ mingo@elte.hu: fixed a similar bug in setup_64.c as well. ]

The breakage was introduced via commit 7d851c8d3db0.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-02-26 12:56:04 +01:00
..
acpi
PCI: don't load acpi_php when acpi is disabled
2008-02-21 15:34:37 -08:00
cpu
x86: fix boot failure on 486 due to TSC breakage
2008-02-26 12:56:04 +01:00
.gitignore
.gitignore update for x86 arch
2007-10-17 21:19:04 +02:00
alternative.c
x86: fix up alternatives with lockdep enabled
2008-01-30 13:33:24 +01:00
aperture_64.c
x86: change aper valid checking sequence
2008-01-30 13:33:39 +01:00
apic_32.c
x86: don't disable the APIC if it hasn't been mapped yet
2008-01-30 13:33:17 +01:00
apic_64.c
x86: change bios_cpu_apicid to percpu data variable fixup
2008-01-30 13:33:21 +01:00
apm_32.c
x86: isolate PIC/PIT in/out calls
2008-01-30 13:33:14 +01:00
asm-offsets_32.c
lguest: fix build breakage
2008-02-26 12:55:49 +01:00
asm-offsets_64.c
x86: add asm_offset PARAVIRT constants
2008-01-30 13:33:19 +01:00
asm-offsets.c
i386: move kernel
2007-10-11 11:17:01 +02:00
audit_64.c
x86_64: move kernel
2007-10-11 11:17:24 +02:00
bootflag.c
x86: coding style cleanup for kernel/bootflag.c
2008-01-30 13:32:31 +01:00
bugs_64.c
x86, 32-bit: trim memory not covered by wb mtrrs
2008-01-30 13:33:18 +01:00
cpuid.c
x86: cpuid, msr: use inode mutex instead of big kernel lock
2008-02-04 16:47:59 +01:00
crash_dump_32.c
kmap leak fix for x86_32 kdump
2007-10-19 11:53:33 -07:00
crash_dump_64.c
Delete filenames in comments.
2007-10-13 10:01:23 -07:00
crash.c
x86: disable hpet legacy replacement for kdump
2007-12-03 17:17:10 +01:00
doublefault_32.c
x86: unify tss_struct
2008-01-30 13:31:31 +01:00
ds.c
x86: fix small sparse warning
2008-01-31 22:05:47 +01:00
e820_32.c
x86_32: trim memory by updating e820
2008-01-30 13:33:32 +01:00
e820_64.c
x86_64: make bootmap_start page align v6
2008-02-01 17:49:41 +01:00
early_printk.c
x86: make early_console static in early_printk.c
2008-02-01 17:49:42 +01:00
early-quirks.c
x86: fix section mismatch warning in early-quirks.c
2008-01-30 13:33:37 +01:00
efi_32.c
x86: sparse error in efi_32.c
2008-02-19 16:18:28 +01:00
efi_64.c
x86: EFI runtime code mapping enhancement
2008-02-13 16:20:35 +01:00
efi_stub_32.S
i386: move kernel
2007-10-11 11:17:01 +02:00
efi_stub_64.S
x86: EFI runtime service support
2008-01-30 13:31:19 +01:00
efi.c
x86: sparse warning in efi.c
2008-02-19 16:18:28 +01:00
entry_32.S
x86: don't make irq_return global
2008-02-19 16:18:29 +01:00
entry_64.S
x86: fix execve with -fstack-protect
2008-02-26 12:55:57 +01:00
genapic_64.c
x86: cleanup x86_cpu_to_apicid references
2008-01-30 13:33:11 +01:00
genapic_flat_64.c
x86: convert cpu_to_apicid to be a per cpu variable
2007-10-19 20:35:03 +02:00
geode_32.c
x86: GEODE: MFGPT: Use "just-in-time" detection for the MFGPT timers
2008-02-09 23:24:08 +01:00
head64.c
x86: zap invalid and unused pmds in early boot
2008-02-18 20:54:14 +01:00
head_32.S
x86: don't make swapper_pg_pmd global
2008-02-26 12:55:58 +01:00
head_64.S
x86: rename KERNEL_TEXT_SIZE => KERNEL_IMAGE_SIZE
2008-02-26 12:55:56 +01:00
hpet.c
x86: hpet fix docbook comment
2008-02-26 12:55:50 +01:00
i386_ksyms_32.c
x86: unexport __{read,write}_lock_failed
2008-01-30 13:30:29 +01:00
i387.c
x86: make mxcsr_feature_mask static again
2008-02-19 16:18:28 +01:00
i8237.c
Driver core: change sysdev classes to use dynamic kobject names
2008-01-24 20:40:40 -08:00
i8253.c
x86: pit_clockevent can be static
2008-02-13 16:20:35 +01:00
i8259_32.c
x86: i8259A: remove redundant irq_descinitialization
2008-02-19 16:18:34 +01:00
i8259_64.c
x86: provide a native_init_IRQ function on 64-bit
2008-01-30 13:33:19 +01:00
init_task.c
x86: nuke a ton of unused exports
2008-01-30 13:30:28 +01:00
io_apic_32.c
arch/x86/kernel/io_apic_{64,32}.c: use time_before
2008-01-30 13:32:19 +01:00
io_apic_64.c
arch/x86/kernel/io_apic_{64,32}.c: use time_before
2008-01-30 13:32:19 +01:00
io_delay.c
x86: unexport io_delay_type
2008-02-19 16:18:29 +01:00
ioport.c
x86: refactor ioport unification
2008-01-30 13:33:10 +01:00
irq_32.c
x86: remove all definitions with fastcall
2008-01-30 13:31:17 +01:00
irq_64.c
x86: rename the struct pt_regs members for 32/64-bit consistency
2008-01-30 13:30:56 +01:00
k8.c
x86_64: move kernel
2007-10-11 11:17:24 +02:00
kdebugfs.c
x86 boot : export boot_params via debugfs for debugging
2008-01-30 13:32:51 +01:00
kprobes.c
x86, kprobes: remove sparse warnings from x86
2008-02-19 16:18:28 +01:00
ldt.c
x86: cleanup - eliminate numbers in LDT allocation code
2008-02-04 16:48:03 +01:00
machine_kexec_32.c
vmcoreinfo: fix the configuration dependencies
2008-02-07 08:42:25 -08:00
machine_kexec_64.c
vmcoreinfo: fix the configuration dependencies
2008-02-07 08:42:25 -08:00
Makefile
x86: exclude vsyscall files from stackprotect
2008-02-19 16:18:32 +01:00
mca_32.c
Delete filenames in comments.
2007-10-13 10:01:23 -07:00
mfgpt_32.c
x86: GEODE: MFGPT: fix typo in printk in mfgpt_timer_setup
2008-02-09 23:24:08 +01:00
microcode.c
x86: fix section mismatch warnings when referencing notifiers
2008-02-01 17:49:42 +01:00
module_32.c
i386: move kernel
2007-10-11 11:17:01 +02:00
module_64.c
x86_64: move kernel
2007-10-11 11:17:24 +02:00
mpparse_32.c
Introduce flags for reserve_bootmem()
2008-02-07 08:42:25 -08:00
mpparse_64.c
x86: fix section mismatch warning in acpi/boot.c
2008-01-30 13:33:37 +01:00
msr.c
x86: cpuid, msr: use inode mutex instead of big kernel lock
2008-02-04 16:47:59 +01:00
nmi_32.c
x86: fix compile warning building without CONFIG_SYSCTL
2008-02-19 16:18:29 +01:00
nmi_64.c
x86: fix compile warning building without CONFIG_SYSCTL
2008-02-19 16:18:29 +01:00
numaq_32.c
x86: convert TSC disabling to generic cpuid disable bitmap
2008-01-30 13:33:20 +01:00
paravirt_patch_32.c
x86: move patching code to arch-specific file.
2008-01-30 13:32:10 +01:00
paravirt_patch_64.c
x86: add stringify header
2008-01-30 13:33:19 +01:00
paravirt.c
x86: fill in missing pv_mmu_ops entries for PAGETABLE_LEVELS >= 3
2008-01-30 13:33:20 +01:00
pci-calgary_64.c
iommu sg: x86: convert calgary IOMMU to use the IOMMU helper
2008-02-05 09:44:11 -08:00
pci-dma_32.c
i386: Clean up duplicate includes in arch/i386/kernel/
2007-10-17 20:15:51 +02:00
pci-dma_64.c
x86: pci-dma_64.c: cleanups
2008-01-30 13:30:31 +01:00
pci-gart_64.c
x86: fix gart_iommu_init()
2008-02-14 23:30:20 +01:00
pci-nommu_64.c
x86 gart: rename iommu.h to gart.h
2007-10-30 00:22:22 +01:00
pci-swiotlb_64.c
x86: nuke a ton of unused exports
2008-01-30 13:30:28 +01:00
pcspeaker.c
i386: move kernel
2007-10-11 11:17:01 +02:00
pmtimer_64.c
x86: move pmtmr related declarations
2008-01-30 13:30:18 +01:00
process_32.c
aout: remove unnecessary inclusions of {asm, linux}/a.out.h
2008-02-08 09:22:30 -08:00
process_64.c
x86: fix execve with -fstack-protect
2008-02-26 12:55:57 +01:00
ptrace.c
x86 ptrace: fix compat PTRACE_SETREGS
2008-02-22 07:35:06 -08:00
quirks.c
Use proper abstractions in quirk_intel_irqbalance
2008-02-11 08:15:03 -08:00
reboot_fixups_32.c
x86: add the RDC machine specific reboot fixup
2008-01-30 13:33:36 +01:00
reboot.c
x86: fixup machine_ops reboot_{32|64}.c unification fallout
2008-02-13 16:20:35 +01:00
relocate_kernel_32.S
i386: move kernel
2007-10-11 11:17:01 +02:00
relocate_kernel_64.S
x86_64: move kernel
2007-10-11 11:17:24 +02:00
rtc.c
x86: fix sched_clock()
2008-01-30 13:32:40 +01:00
scx200_32.c
x86: fix sparse warning in kernel/scx200_32.c
2008-01-31 22:05:45 +01:00
setup64.c
x86: export __supported_pte_mask
2008-01-30 13:33:24 +01:00
setup_32.c
remove mca-pentium
2008-02-19 16:18:28 +01:00
setup_64.c
x86: fix boot failure on 486 due to TSC breakage
2008-02-26 12:56:04 +01:00
sigframe_32.h
i386: move kernel
2007-10-11 11:17:01 +02:00
signal_32.c
x86: remove unneded casts
2008-01-30 13:33:23 +01:00
signal_64.c
x86: print which shared library/executable faulted in segfault etc. messages v3
2008-01-30 13:33:18 +01:00
smp_32.c
x86: voluntary leave_mm before entering ACPI C3
2008-01-30 13:32:01 +01:00
smp_64.c
x86: voluntary leave_mm before entering ACPI C3
2008-01-30 13:32:01 +01:00
smpboot_32.c
calibrate_delay() must be __cpuinit
2008-02-06 10:41:08 -08:00
smpboot_64.c
x86: make c_idle.work have a static address.
2008-02-26 12:56:02 +01:00
smpcommon_32.c
x86: change write_gdt_entry signature.
2008-01-30 13:31:13 +01:00
srat_32.c
Merge branches 'release', 'bugzilla-6217', 'bugzilla-6629', 'bugzilla-6933', 'bugzilla-7186', 'bugzilla-8269', 'bugzilla-8570', 'bugzilla-9139', 'bugzilla-9277', 'bugzilla-9341', 'bugzilla-9444', 'bugzilla-9614', 'bugzilla-9643' and 'bugzilla-9644' into release
2008-02-07 03:09:43 -05:00
stacktrace.c
x86: don't save unreliable stack trace entries
2008-02-26 12:55:58 +01:00
step.c
x86: remove last user of get_segment_eip
2008-01-30 13:33:12 +01:00
summit_32.c
spelling fixes: arch/i386/
2007-10-20 01:13:56 +02:00
sys_i386_32.c
remove include/asm-*/ipc.h
2007-10-17 08:42:55 -07:00
sys_x86_64.c
x86: PIE executable randomization, checkpatch fixes
2008-01-30 13:31:07 +01:00
syscall_64.c
i386/x86_64: move headers to include/asm-x86
2007-10-11 11:20:03 +02:00
syscall_table_32.S
timerfd: wire the new timerfd API to the x86 family
2008-02-05 09:44:07 -08:00
tce_64.c
x86: Create clflush() inline, remove hardcoded wbinvd
2007-10-17 20:16:12 +02:00
test_nx.c
x86: mark the .rodata section also NX
2008-02-06 22:39:45 +01:00
test_rodata.c
x86: include proper prototypes for rodata_test
2008-02-14 23:30:20 +01:00
time_32.c
x86: rename the struct pt_regs members for 32/64-bit consistency
2008-01-30 13:30:56 +01:00
time_64.c
time: fix typo in comments
2008-02-08 09:22:29 -08:00
tls.c
x86: x86 user_regset TLS
2008-01-30 13:31:52 +01:00
tls.h
x86: x86 user_regset TLS
2008-01-30 13:31:52 +01:00
topology.c
x86: fix section mismatch warning in topology.c:arch_register_cpu
2008-02-19 16:18:30 +01:00
trampoline_32.S
x86: remove misleading comments in trampoline_*.S
2008-02-04 16:48:01 +01:00
trampoline_64.S
x86: remove misleading comments in trampoline_*.S
2008-02-04 16:48:01 +01:00
traps_32.c
x86: fix sparse error in traps_32.c
2008-02-06 22:39:44 +01:00
traps_64.c
x86: fix "BUG: sleeping function called from invalid context" in print_vma_addr()
2008-02-14 23:30:19 +01:00
tsc_32.c
x86: notsc is ignored on common configurations
2008-02-26 12:55:54 +01:00
tsc_64.c
x86: export check_tsc_unstable
2008-01-30 13:33:24 +01:00
tsc_sync.c
x86: add warning to check_tsc_warp()
2008-01-30 13:33:24 +01:00
verify_cpu_64.S
x86_64: move kernel
2007-10-11 11:17:24 +02:00
vm86_32.c
arch/x86/: spelling fixes
2008-01-30 13:31:42 +01:00
vmi_32.c
x86: VMI fix
2008-02-04 16:47:54 +01:00
vmiclock_32.c
x86: isolate PIC/PIT in/out calls
2008-01-30 13:33:14 +01:00
vmlinux_32.lds.S
x86: lds - Use PAGE_SIZE instead of numeric constant
2008-02-19 16:18:33 +01:00
vmlinux_64.lds.S
x86: lds - Use THREAD_SIZE instead of numeric constant
2008-02-19 16:18:34 +01:00
vmlinux.lds.S
i386: move kernel
2007-10-11 11:17:01 +02:00
vsmp_64.c
x86: clean up arch/x86/kernel/vsmp_64.c
2008-01-30 13:30:24 +01:00
vsyscall_64.c
x86: fix vsyscall wreckage
2008-02-26 12:55:57 +01:00
x8664_ksyms_64.c
x86: export cpu_gdt_descr
2008-01-30 13:31:10 +01:00