x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

Otherwise arch_task_struct_size == 0 and we die.  While we're at it,
set X86_FEATURE_ALWAYS, too.

Reported-by: David Saggiorato <david@saggiorato.net>
Tested-by: David Saggiorato <david@saggiorato.net>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: aaeb5c01c5b ("x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
Link: http://lkml.kernel.org/r/8de723afbf0811071185039f9088733188b606c9.1475103911.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/cpu/common.c

@@ -804,21 +804,20 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		identify_cpu_without_cpuid(c);
 
 	/* cyrix could have cpuid enabled via c_identify()*/
-	if (!have_cpuid_p())
-		return;
+	if (have_cpuid_p()) {
+		cpu_detect(c);
+		get_cpu_vendor(c);
+		get_cpu_cap(c);
 
-	cpu_detect(c);
-	get_cpu_vendor(c);
-	get_cpu_cap(c);
+		if (this_cpu->c_early_init)
+			this_cpu->c_early_init(c);
 
-	if (this_cpu->c_early_init)
-		this_cpu->c_early_init(c);
+		c->cpu_index = 0;
+		filter_cpuid_features(c, false);
 
-	c->cpu_index = 0;
-	filter_cpuid_features(c, false);
-
-	if (this_cpu->c_bsp_init)
-		this_cpu->c_bsp_init(c);
+		if (this_cpu->c_bsp_init)
+			this_cpu->c_bsp_init(c);
+	}
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 	fpu__init_system(c);