On Tue, 30 Sep 2014, Bryan O'Donoghue wrote:
> static void default_init(struct cpuinfo_x86 *c)
> {
> -#ifdef CONFIG_X86_64
> cpu_detect_cache_sizes(c);
> -#else
> +
> /* Not much we can do here... */
> /* Check if at least it has cpuid */
> if (c->cpuid_level == -1) {
> @@ -79,7 +78,6 @@ static void default_init(struct cpuinfo_x86 *c)
> else if (c->x86 == 3)
> strcpy(c->x86_model_id, "386");
> }
> -#endif
What's the exact point of this? This is the default init function
which is for X86_VENDOR_UNKNOWN, right?
> }
>
> static const struct cpu_dev default_cpu = {
> @@ -874,6 +872,15 @@ static void identify_cpu(struct cpuinfo_x86 *c)
> #endif
>
> /*
> + * If c_x86_vendor != X86_VENDOR_UNKNOWN i.e. a known vendor then
> + * there's a vendor specific c_init()
> + *
> + * Even still Intel, AMD and VIA make use of legacy_cache_size which
> + * is reachable only through default_init right now
That's nonsense. It's called from cpu_detect_cache_sizes() and that is
called from:
arch/x86/kernel/cpu/amd.c: cpu_detect_cache_sizes(c);
arch/x86/kernel/cpu/centaur.c: cpu_detect_cache_sizes(c);
arch/x86/kernel/cpu/common.c: cpu_detect_cache_sizes(c);
arch/x86/kernel/cpu/cyrix.c: cpu_detect_cache_sizes(c);
arch/x86/kernel/cpu/transmeta.c: cpu_detect_cache_sizes(c);
So we have 4 callsites outside of default_init() already. Now you're
adding another one into identify_cpu()
> + */
> + if (this_cpu->c_x86_vendor != X86_VENDOR_UNKNOWN)
> + default_init(c);
With the consequence that for amd/centaur/cyrix/transmeta
cpu_detect_cache_sizes() is invoked twice for nothing.
So the only CPU vendor c_init() callback which does not call
cpu_detect_cache_sizes() is the Intel one. And therefor we inflict
that call on all others twice. Brilliant solution!
So the proper solution is to add the call to identify_cpu()
unconditionally and remove it from _all_ other call sites, make it
static and be done with it.
Sigh,
tglx
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