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SubjectRe: [PATCH] x86: better CPU identification without the CPUID
On Sat, Sep 13, 2008 at 9:43 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
> On Sat, Sep 13, 2008 at 3:56 AM, Krzysztof Helt <krzysztof.h1@wp.pl> wrote:
>> 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

I updated it to tip/master and call that in early_identify_cpu. it
should solve mtrr detection for Cyrix ...

Please check attached patch.

Thanks

YH
[PATCH] x86: identify_cpu_without_cpuid

need to call c_identify() for cpus without cpuid earlier...

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>

---
arch/x86/kernel/cpu/common.c | 63 +++++++++++++++++++++++++++----------------
1 file changed, 40 insertions(+), 23 deletions(-)

Index: linux-2.6/arch/x86/kernel/cpu/common.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/common.c
+++ linux-2.6/arch/x86/kernel/cpu/common.c
@@ -485,6 +485,33 @@ static void __cpuinit get_cpu_cap(struct
c->x86_power = cpuid_edx(0x80000007);

}
+
+static void __cpuinit identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_X86_32
+ int i;
+
+ /*
+ * First of all, decide if this is a 486 or higher
+ * It's a 486 if we can modify the AC flag
+ */
+ if (flag_is_changeable_p(X86_EFLAGS_AC))
+ c->x86 = 4;
+ else
+ c->x86 = 3;
+
+ 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);
+ break;
+ }
+ }
+#endif
+}
+
/*
* Do minimum CPU detection early.
* Fields really needed: vendor, cpuid_level, family, model, mask,
@@ -503,18 +530,17 @@ static void __init early_identify_cpu(st
#endif
c->x86_cache_alignment = c->x86_clflush_size;

- if (!have_cpuid_p())
- return;
-
memset(&c->x86_capability, 0, sizeof c->x86_capability);
-
c->extended_cpuid_level = 0;

- cpu_detect(c);
-
- get_cpu_vendor(c);
-
- get_cpu_cap(c);
+ if (!have_cpuid_p()) {
+ identify_cpu_without_cpuid(c);
+ return;
+ } else {
+ cpu_detect(c);
+ get_cpu_vendor(c);
+ get_cpu_cap(c);
+ }

if (this_cpu->c_early_init)
this_cpu->c_early_init(c);
@@ -583,11 +609,13 @@ static void __cpuinit detect_nopl(struct

static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
{
- if (!have_cpuid_p())
- return;
-
c->extended_cpuid_level = 0;

+ if (!have_cpuid_p()) {
+ identify_cpu_without_cpuid(c);
+ return;
+ }
+
cpu_detect(c);

get_cpu_vendor(c);
@@ -639,17 +667,6 @@ static void __cpuinit identify_cpu(struc
c->x86_cache_alignment = c->x86_clflush_size;
memset(&c->x86_capability, 0, sizeof c->x86_capability);

- if (!have_cpuid_p()) {
- /*
- * First of all, decide if this is a 486 or higher
- * It's a 486 if we can modify the AC flag
- */
- if (flag_is_changeable_p(X86_EFLAGS_AC))
- c->x86 = 4;
- else
- c->x86 = 3;
- }
-
generic_identify(c);

if (this_cpu->c_identify)
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