Messages in this thread Patches in this message | | | Date | Thu, 17 May 2007 23:28:01 +0200 | From | Christian Volkmann <> | Subject | Re: 2.6.22-rc1 does not boot on VIA C3_2 cause of X86_CMPXCHG64 |
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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.
- middle term solution already planed: introduce arch/i386/boot/cpucheck.c
To be done by somebody with more detail knowledge than me: (never did x86 assembler before)
- I add "# missed before: set ds" => somebody should check if I am right with the way to set. => seems to be a generic error in setup.S not to set "ds" for error messages.
- other X86-CPU than AMD (?) or Intel => correct verify_cpu.S or set bits if required.
Best regards,
Christian
--- arch/i386/kernel/verify_cpu.S 2007-05-17 05:17:40.000000000 +0200 +++ arch/i386/kernel/verify_cpu.S 2007-05-17 23:14:18.266679323 +0200 @@ -54,6 +54,12 @@
andl $REQUIRED_MASK1,%edx xorl $REQUIRED_MASK1,%edx +/* VIAC3 does not report the existing CMPXCHG64 by default. So do not go to bad for CMPXCHG64 for this */ +/* via C3 EBGA datasheet R1.9 tells the command works also without shown bit. */ +#if CONFIG_MVIAC3_2 + andl $~NEED_CMPXCHG64,%edx +#endif + jnz bad #endif /* REQUIRED_MASK1 */
--- arch/i386/boot/setup.S 2007-05-17 21:53:08.009226208 +0200 +++ arch/i386/boot/setup.S 2007-05-17 23:12:36.815989168 +0200 @@ -310,12 +310,15 @@ call verify_cpu testl %eax,%eax jz cpu_ok + # missed before: set ds + movw %cs, %ax # aka SETUPSEG + movw %ax, %ds lea cpu_panic_mess,%si call prtstr 1: jmp 1b
cpu_panic_mess: - .asciz "PANIC: CPU too old for this kernel." + .asciz "PANIC: CPU too old for this kernel or CPUID function bits are wrong."
#include "../kernel/verify_cpu.S"
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