x86/cpufeature: Replace the old static_cpu_has() with safe variant

So the old one didn't work properly before alternatives had run.
And it was supposed to provide an optimized JMP because the
assumption was that the offset it is jumping to is within a
signed byte and thus a two-byte JMP.

So I did an x86_64 allyesconfig build and dumped all possible
sites where static_cpu_has() was used. The optimization amounted
to all in all 12(!) places where static_cpu_has() had generated
a 2-byte JMP. Which has saved us a whopping 36 bytes!

This clearly is not worth the trouble so we can remove it. The
only place where the optimization might count - in __switch_to()
- we will handle differently. But that's not subject of this
patch.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1453842730-28463-6-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 5 insertions, 13 deletions

diff --git a/arch/x86/kernel/apic/apic_numachip.c b/arch/x86/kernel/apic/apic_numachip.c
index c80c02c6ec49..ab5c2c685a3c 100644
--- a/arch/x86/kernel/apic/apic_numachip.c
+++ b/arch/x86/kernel/apic/apic_numachip.c
@@ -30,7 +30,7 @@ static unsigned int numachip1_get_apic_id(unsigned long x)
         unsigned long value;
         unsigned int id = (x >> 24) & 0xff;
 
-        if (static_cpu_has_safe(X86_FEATURE_NODEID_MSR)) {
+        if (static_cpu_has(X86_FEATURE_NODEID_MSR)) {
                 rdmsrl(MSR_FAM10H_NODE_ID, value);
                 id |= (value << 2) & 0xff00;
         }
@@ -178,7 +178,7 @@ static void fixup_cpu_id(struct cpuinfo_x86 *c, int node)
         this_cpu_write(cpu_llc_id, node);
 
         /* Account for nodes per socket in multi-core-module processors */
-        if (static_cpu_has_safe(X86_FEATURE_NODEID_MSR)) {
+        if (static_cpu_has(X86_FEATURE_NODEID_MSR)) {
                 rdmsrl(MSR_FAM10H_NODE_ID, val);
                 nodes = ((val >> 3) & 7) + 1;
         }
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 37830de8f60a..ee499817f3f5 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1475,19 +1475,11 @@ void cpu_init(void)
 }
 #endif
 
-#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS
-void warn_pre_alternatives(void)
-{
-        WARN(1, "You're using static_cpu_has before alternatives have run!\n");
-}
-EXPORT_SYMBOL_GPL(warn_pre_alternatives);
-#endif
-
-inline bool __static_cpu_has_safe(u16 bit)
+inline bool __static_cpu_has(u16 bit)
 {
         return boot_cpu_has(bit);
 }
-EXPORT_SYMBOL_GPL(__static_cpu_has_safe);
+EXPORT_SYMBOL_GPL(__static_cpu_has);
 
 static void bsp_resume(void)
 {
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index e574b8546518..3dce1ca0a653 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -362,7 +362,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
         /* make room for real-mode segments */
         tsk->thread.sp0 += 16;
 
-        if (static_cpu_has_safe(X86_FEATURE_SEP))
+        if (static_cpu_has(X86_FEATURE_SEP))
                 tsk->thread.sysenter_cs = 0;
 
         load_sp0(tss, &tsk->thread);