x86/cpufeatures: Remove get_scattered_cpuid_leaf()

get_scattered_cpuid_leaf() was added[1] to help KVM rebuild hardware-
defined leafs that are rearranged by Linux to avoid bloating the
x86_capability array. Eventually, the last consumer of the function was
removed[2], but the function itself was kept, perhaps even intentionally
as a form of documentation.

Remove get_scattered_cpuid_leaf() as it is currently not used by KVM.
Furthermore, simply rebuilding the "real" leaf does not resolve all of
KVM's woes when it comes to exposing a scattered CPUID feature, i.e.
keeping the function as documentation may be counter-productive in some
scenarios, e.g. when KVM needs to do more than simply expose the leaf.

[1] 47bdf337 ("x86/cpuid: Provide get_scattered_cpuid_leaf()")
[2] b7b27aa0 ("KVM/x86: Update the reverse_cpuid list to include CPUID_7_EDX")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ingo Molnar <mingo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/20181105185725.18679-1-sean.j.christopherson@intel.com

arch/x86/kernel/cpu/cpu.h

@@ -49,9 +49,6 @@ extern void get_cpu_cap(struct cpuinfo_x86 *c);
 extern void get_cpu_address_sizes(struct cpuinfo_x86 *c);
 extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
 extern void init_scattered_cpuid_features(struct cpuinfo_x86 *c);
-extern u32 get_scattered_cpuid_leaf(unsigned int level,
-				    unsigned int sub_leaf,
-				    enum cpuid_regs_idx reg);
 extern void init_intel_cacheinfo(struct cpuinfo_x86 *c);
 extern void init_amd_cacheinfo(struct cpuinfo_x86 *c);
 extern void init_hygon_cacheinfo(struct cpuinfo_x86 *c);

arch/x86/kernel/cpu/scattered.c

@@ -56,27 +56,3 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 			set_cpu_cap(c, cb->feature);
 	}
 }
-
-u32 get_scattered_cpuid_leaf(unsigned int level, unsigned int sub_leaf,
-			     enum cpuid_regs_idx reg)
-{
-	const struct cpuid_bit *cb;
-	u32 cpuid_val = 0;
-
-	for (cb = cpuid_bits; cb->feature; cb++) {
-
-		if (level > cb->level)
-			continue;
-
-		if (level < cb->level)
-			break;
-
-		if (reg == cb->reg && sub_leaf == cb->sub_leaf) {
-			if (cpu_has(&boot_cpu_data, cb->feature))
-				cpuid_val |= BIT(cb->bit);
-		}
-	}
-
-	return cpuid_val;
-}
-EXPORT_SYMBOL_GPL(get_scattered_cpuid_leaf);