x86: identify_cpu_without_cpuid v2

Krzysztof found some old cyrix cpu where an mtrr-alike cpu feature was
not detected properly.

this one is based on Krzysztof' patch, and we call ->c_identify() in
early_identify_cpu.

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

v2: Krzysztof point out need to give cyrix another chance about cpuid
    checking again, after ->c_identify() enables cpuid for it

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 40 insertions, 17 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9a57106c1995..f5f25b85be95 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -485,6 +485,33 @@ static void __cpuinit get_cpu_cap(struct cpuinfo_x86 *c)
                 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,
@@ -503,13 +530,16 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 #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;
 
+        if (!have_cpuid_p())
+                identify_cpu_without_cpuid(c);
+
+        /* cyrix could have cpuid enabled via c_identify()*/
+        if (!have_cpuid())
+                return;
+
         cpu_detect(c);
 
         get_cpu_vendor(c);
@@ -583,10 +613,14 @@ static void __cpuinit detect_nopl(struct cpuinfo_x86 *c)
 
 static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
 {
+        c->extended_cpuid_level = 0;
+
         if (!have_cpuid_p())
-                return;
+                identify_cpu_without_cpuid(c);
 
-        c->extended_cpuid_level = 0;
+        /* cyrix could have cpuid enabled via c_identify()*/
+        if (!have_cpuid())
+                return;
 
         cpu_detect(c);
 
@@ -639,17 +673,6 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
         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)