x86: use ELF section to list CPU vendor specific code

Replace the hardcoded list of initialization functions for each CPU
vendor by a list in an ELF section, which is read at initialization in
arch/x86/kernel/cpu/cpu.c to fill the cpu_devs[] array. The ELF
section, named .x86cpuvendor.init, is reclaimed after boot, and
contains entries of type "struct cpu_vendor_dev" which associates a
vendor number with a pointer to a "struct cpu_dev" structure.

This first modification allows to remove all the VENDOR_init_cpu()
functions.

This patch also removes the hardcoded calls to early_init_amd() and
early_init_intel(). Instead, we add a "c_early_init" member to the
cpu_dev structure, which is then called if not NULL by the generic CPU
initialization code. Unfortunately, in early_cpu_detect(), this_cpu is
not yet set, so we have to use the cpu_devs[] array directly.

This patch is part of the Linux Tiny project, and is needed for
further patch that will allow to disable compilation of unused CPU
support code.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 10 insertions, 23 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a38aafaefc23..0fd6be154d5d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -328,14 +328,9 @@ static void __init early_cpu_detect(void)
 
         get_cpu_vendor(c, 1);
 
-        switch (c->x86_vendor) {
-        case X86_VENDOR_AMD:
-                early_init_amd(c);
-                break;
-        case X86_VENDOR_INTEL:
-                early_init_intel(c);
-                break;
-        }
+        if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
+            cpu_devs[c->x86_vendor]->c_early_init)
+                cpu_devs[c->x86_vendor]->c_early_init(c);
 
         early_get_cap(c);
 }
@@ -616,23 +611,15 @@ __setup("clearcpuid=", setup_disablecpuid);
 
 cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;
 
-/* This is hacky. :)
- * We're emulating future behavior.
- * In the future, the cpu-specific init functions will be called implicitly
- * via the magic of initcalls.
- * They will insert themselves into the cpu_devs structure.
- * Then, when cpu_init() is called, we can just iterate over that array.
- */
 void __init early_cpu_init(void)
 {
-        intel_cpu_init();
-        cyrix_init_cpu();
-        nsc_init_cpu();
-        amd_init_cpu();
-        centaur_init_cpu();
-        transmeta_init_cpu();
-        nexgen_init_cpu();
-        umc_init_cpu();
+        struct cpu_vendor_dev *cvdev;
+
+        for (cvdev = __x86cpuvendor_start ;
+             cvdev < __x86cpuvendor_end   ;
+             cvdev++)
+                cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
+
         early_cpu_detect();
 }