x86: APIC: remove apic_write_around(); use alternatives

Use alternatives to select the workaround for the 11AP Pentium erratum
for the affected steppings on the fly rather than build time.  Remove the
X86_GOOD_APIC configuration option and replace all the calls to
apic_write_around() with plain apic_write(), protecting accesses to the
ESR as appropriate due to the 3AP Pentium erratum.  Remove
apic_read_around() and all its invocations altogether as not needed.
Remove apic_write_atomic() and all its implementing backends.  The use of
ASM_OUTPUT2() is not strictly needed for input constraints, but I have
used it for readability's sake.

I had the feeling no one else was brave enough to do it, so I went ahead
and here it is.  Verified by checking the generated assembly and tested
with both a 32-bit and a 64-bit configuration, also with the 11AP
"feature" forced on and verified with gdb on /proc/kcore to work as
expected (as an 11AP machines are quite hard to get hands on these days).
Some script complained about the use of "volatile", but apic_write() needs
it for the same reason and is effectively a replacement for writel(), so I
have disregarded it.

I am not sure what the policy wrt defconfig files is, they are generated
and there is risk of a conflict resulting from an unrelated change, so I
have left changes to them out.  The option will get removed from them at
the next run.

Some testing with machines other than mine will be needed to avoid some
stupid mistake, but despite its volume, the change is not really that
intrusive, so I am fairly confident that because it works for me, it will
everywhere.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

7 files changed, 16 insertions, 31 deletions

diff --git a/include/asm-x86/apic.h b/include/asm-x86/apic.h
index 4e2c1e517f0..ea866baccef 100644
--- a/include/asm-x86/apic.h
+++ b/include/asm-x86/apic.h
@@ -3,6 +3,8 @@
 
 #include <linux/pm.h>
 #include <linux/delay.h>
+
+#include <asm/alternative.h>
 #include <asm/fixmap.h>
 #include <asm/apicdef.h>
 #include <asm/processor.h>
@@ -48,7 +50,6 @@ extern int disable_apic;
 #include <asm/paravirt.h>
 #else
 #define apic_write native_apic_write
-#define apic_write_atomic native_apic_write_atomic
 #define apic_read native_apic_read
 #define setup_boot_clock setup_boot_APIC_clock
 #define setup_secondary_clock setup_secondary_APIC_clock
@@ -58,12 +59,11 @@ extern int is_vsmp_box(void);
 
 static inline void native_apic_write(unsigned long reg, u32 v)
 {
-	*((volatile u32 *)(APIC_BASE + reg)) = v;
-}
+	volatile u32 *addr = (volatile u32 *)(APIC_BASE + reg);
 
-static inline void native_apic_write_atomic(unsigned long reg, u32 v)
-{
-	(void)xchg((u32 *)(APIC_BASE + reg), v);
+	alternative_io("movl %0, %1", "xchgl %0, %1", X86_FEATURE_11AP,
+		       ASM_OUTPUT2("=r" (v), "=m" (*addr)),
+		       ASM_OUTPUT2("0" (v), "m" (*addr)));
 }
 
 static inline u32 native_apic_read(unsigned long reg)
@@ -75,16 +75,6 @@ extern void apic_wait_icr_idle(void);
 extern u32 safe_apic_wait_icr_idle(void);
 extern int get_physical_broadcast(void);
 
-#ifdef CONFIG_X86_GOOD_APIC
-# define FORCE_READ_AROUND_WRITE 0
-# define apic_read_around(x)
-# define apic_write_around(x, y) apic_write((x), (y))
-#else
-# define FORCE_READ_AROUND_WRITE 1
-# define apic_read_around(x) apic_read(x)
-# define apic_write_around(x, y) apic_write_atomic((x), (y))
-#endif
-
 static inline void ack_APIC_irq(void)
 {
 	/*
@@ -95,7 +85,7 @@ static inline void ack_APIC_irq(void)
 	 */
 
 	/* Docs say use 0 for future compatibility */
-	apic_write_around(APIC_EOI, 0);
+	apic_write(APIC_EOI, 0);
 }
 
 extern int lapic_get_maxlvt(void);
diff --git a/include/asm-x86/cpufeature.h b/include/asm-x86/cpufeature.h
index 75ef959db32..2f5a792b0ac 100644
--- a/include/asm-x86/cpufeature.h
+++ b/include/asm-x86/cpufeature.h
@@ -79,6 +79,7 @@
 #define X86_FEATURE_REP_GOOD	(3*32+16) /* rep microcode works well on this CPU */
 #define X86_FEATURE_MFENCE_RDTSC (3*32+17) /* Mfence synchronizes RDTSC */
 #define X86_FEATURE_LFENCE_RDTSC (3*32+18) /* Lfence synchronizes RDTSC */
+#define X86_FEATURE_11AP	(3*32+19)  /* Bad local APIC aka 11AP */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3	(4*32+ 0) /* Streaming SIMD Extensions-3 */
diff --git a/include/asm-x86/mach-bigsmp/mach_apic.h b/include/asm-x86/mach-bigsmp/mach_apic.h
index 017c8c19ad8..c3b9dc6970c 100644
--- a/include/asm-x86/mach-bigsmp/mach_apic.h
+++ b/include/asm-x86/mach-bigsmp/mach_apic.h
@@ -63,9 +63,9 @@ static inline void init_apic_ldr(void)
 	unsigned long val;
 	int cpu = smp_processor_id();
 
-	apic_write_around(APIC_DFR, APIC_DFR_VALUE);
+	apic_write(APIC_DFR, APIC_DFR_VALUE);
 	val = calculate_ldr(cpu);
-	apic_write_around(APIC_LDR, val);
+	apic_write(APIC_LDR, val);
 }
 
 static inline void setup_apic_routing(void)
diff --git a/include/asm-x86/mach-default/mach_apic.h b/include/asm-x86/mach-default/mach_apic.h
index 0b2cde5e1b7..f3226b9a6b8 100644
--- a/include/asm-x86/mach-default/mach_apic.h
+++ b/include/asm-x86/mach-default/mach_apic.h
@@ -46,10 +46,10 @@ static inline void init_apic_ldr(void)
 {
 	unsigned long val;
 
-	apic_write_around(APIC_DFR, APIC_DFR_VALUE);
+	apic_write(APIC_DFR, APIC_DFR_VALUE);
 	val = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
 	val |= SET_APIC_LOGICAL_ID(1UL << smp_processor_id());
-	apic_write_around(APIC_LDR, val);
+	apic_write(APIC_LDR, val);
 }
 
 static inline int apic_id_registered(void)
diff --git a/include/asm-x86/mach-es7000/mach_apic.h b/include/asm-x86/mach-es7000/mach_apic.h
index fbc8ad256f5..0a3fdf93067 100644
--- a/include/asm-x86/mach-es7000/mach_apic.h
+++ b/include/asm-x86/mach-es7000/mach_apic.h
@@ -66,9 +66,9 @@ static inline void init_apic_ldr(void)
 	unsigned long val;
 	int cpu = smp_processor_id();
 
-	apic_write_around(APIC_DFR, APIC_DFR_VALUE);
+	apic_write(APIC_DFR, APIC_DFR_VALUE);
 	val = calculate_ldr(cpu);
-	apic_write_around(APIC_LDR, val);
+	apic_write(APIC_LDR, val);
 }
 
 #ifndef CONFIG_X86_GENERICARCH
diff --git a/include/asm-x86/mach-summit/mach_apic.h b/include/asm-x86/mach-summit/mach_apic.h
index 1f76c2e7023..75d2c95005d 100644
--- a/include/asm-x86/mach-summit/mach_apic.h
+++ b/include/asm-x86/mach-summit/mach_apic.h
@@ -63,10 +63,10 @@ static inline void init_apic_ldr(void)
 	 * BIOS puts 5 CPUs in one APIC cluster, we're hosed. */
 	BUG_ON(count >= XAPIC_DEST_CPUS_SHIFT);
 	id = my_cluster | (1UL << count);
-	apic_write_around(APIC_DFR, APIC_DFR_VALUE);
+	apic_write(APIC_DFR, APIC_DFR_VALUE);
 	val = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
 	val |= SET_APIC_LOGICAL_ID(id);
-	apic_write_around(APIC_LDR, val);
+	apic_write(APIC_LDR, val);
 }
 
 static inline int multi_timer_check(int apic, int irq)
diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
index ef5e8ec6a6a..719d959d0bc 100644
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -205,7 +205,6 @@ struct pv_apic_ops {
 	 * these shouldn't be in this interface.
 	 */
 	void (*apic_write)(unsigned long reg, u32 v);
-	void (*apic_write_atomic)(unsigned long reg, u32 v);
 	u32 (*apic_read)(unsigned long reg);
 	void (*setup_boot_clock)(void);
 	void (*setup_secondary_clock)(void);
@@ -896,11 +895,6 @@ static inline void apic_write(unsigned long reg, u32 v)
 	PVOP_VCALL2(pv_apic_ops.apic_write, reg, v);
 }
 
-static inline void apic_write_atomic(unsigned long reg, u32 v)
-{
-	PVOP_VCALL2(pv_apic_ops.apic_write_atomic, reg, v);
-}
-
 static inline u32 apic_read(unsigned long reg)
 {
 	return PVOP_CALL1(unsigned long, pv_apic_ops.apic_read, reg);