Re: 2.6.22-rc1 does not boot on VIA C3_2 cause of X86_CMPXCHG64

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Christian Volkmann wrote:
Christian wrote:
Hmm, I really think so...:
May I brought up a wrong reason with the command cmpxchg64.
But disabling CONFIG_X86_CMPXCHG64 helps.



Hi,


I found some time to investigate. My resume is:

- kernel/verify_cpu.S causes the stop at boot time
  Cause the required flag for CMPXCHG8B is not set.

- boot/setup.S did not print "PANIC: CPU too old for this kernel"
  ( not visible, also the message did not match )

- VIA C3_2: CMPXCHG8B should work always. Via C3 EBGA Datasheet R1.90 page 30 (3-4)
  But the bit is not set cause of some early Win NT bugs.

- X86_CMPXCHG64 can be set and used. Just verify_cpu.S requires a change
  to ignore the missing indicator at boot time.



My suggestion for the fix is:

- kernel/verify_cpu.S should be more tolerant if CONFIG_MVIAC3_2 is set
  ( see patch below )

- boot/setup.S should be fixed to print out a proper error message
  ( see below )

- X86_CMPXCHG64 patch(earlier mail in thread ) should not be used.


- Important: somebody to check other CPU types if the same behavior happens.

I applied the patch on rc2, changed 'if CONFIG_MVIAC3_2' in if CONFIG_MVIAC7' and build a working VIA C7 kernel.

--
Hans
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