Messages in this thread Patch in this message | | | Date | Sat, 13 Sep 2008 12:56:06 +0200 | From | Krzysztof Helt <> | Subject | [PATCH] x86: better CPU identification without the CPUID |
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From: Krzysztof Helt <krzysztof.h1@wp.pl>
cpus without the CPUID instruction are identified as general 386 or 486 while some cpus (mostly made by Cyrix) provide c_identify function which identify correctly older cpus using cpu specific registers).
Cyrix cpus are even worse as 5x86 and 6x68 have the CPUID instruction disabled. The CPUID is enabled by the c_identify() but the c_identify is only called when the CPUID is available.
Fix this by calling the c_identify() for all known cpu families if there is no the CPUID instruction
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl> ---
I have tested it on Cyrix Cx486DX2 cpu.
I suspect that coma_bug field and mtrr support is not set correctly for the Cyrix 6x86 family. I have not a cpu from the Cyrix 6x68 family to test.
The code path is (+ where the patch code is added)
if (have_cpuid_p()) {
} + } else { ... + }
so it does not affect cpus with the CPUID instruction.
Regards, Krzysztof
diff -urp linux-mm/arch/x86/kernel/cpu/common.c linux-486/arch/x86/kernel/cpu/common.c --- linux-mm/arch/x86/kernel/cpu/common.c 2008-09-05 23:38:20.295563396 +0200 +++ linux-486/arch/x86/kernel/cpu/common.c 2008-09-12 22:53:27.062265329 +0200 @@ -444,6 +444,17 @@ static void __cpuinit generic_identify(s init_scattered_cpuid_features(c); detect_nopl(c); + } else { + int i; + for (i = 0; i < X86_VENDOR_NUM; i++) + if (cpu_devs[i] && cpu_devs[i]->c_identify) { + c->x86_vendor_id[0] = 0; + cpu_devs[i]->c_identify(c); + if (c->x86_vendor_id[0]) { + get_cpu_vendor(c, 0); + break; + } + } } }
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