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>

1 files changed, 19 insertions, 30 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 687376ab07e8..f251f5c38823 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -546,8 +546,8 @@ static inline void __inquire_remote_apic(int apicid)
                         printk(KERN_CONT
                                "a previous APIC delivery may have failed\n");
 
-                apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(apicid));
-                apic_write_around(APIC_ICR, APIC_DM_REMRD | regs[i]);
+                apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(apicid));
+                apic_write(APIC_ICR, APIC_DM_REMRD | regs[i]);
 
                 timeout = 0;
                 do {
@@ -579,11 +579,11 @@ wakeup_secondary_cpu(int logical_apicid, unsigned long start_eip)
         int maxlvt;
 
         /* Target chip */
-        apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(logical_apicid));
+        apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(logical_apicid));
 
         /* Boot on the stack */
         /* Kick the second */
-        apic_write_around(APIC_ICR, APIC_DM_NMI | APIC_DEST_LOGICAL);
+        apic_write(APIC_ICR, APIC_DM_NMI | APIC_DEST_LOGICAL);
 
         Dprintk("Waiting for send to finish...\n");
         send_status = safe_apic_wait_icr_idle();
@@ -592,14 +592,9 @@ wakeup_secondary_cpu(int logical_apicid, unsigned long start_eip)
          * Give the other CPU some time to accept the IPI.
          */
         udelay(200);
-        /*
-         * Due to the Pentium erratum 3AP.
-         */
         maxlvt = lapic_get_maxlvt();
-        if (maxlvt > 3) {
-                apic_read_around(APIC_SPIV);
+        if (maxlvt > 3)                 /* Due to the Pentium erratum 3AP.  */
                 apic_write(APIC_ESR, 0);
-        }
         accept_status = (apic_read(APIC_ESR) & 0xEF);
         Dprintk("NMI sent.\n");
 
@@ -625,12 +620,14 @@ wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
                 return send_status;
         }
 
+        maxlvt = lapic_get_maxlvt();
+
         /*
          * Be paranoid about clearing APIC errors.
          */
         if (APIC_INTEGRATED(apic_version[phys_apicid])) {
-                apic_read_around(APIC_SPIV);
-                apic_write(APIC_ESR, 0);
+                if (maxlvt > 3)         /* Due to the Pentium erratum 3AP.  */
+                        apic_write(APIC_ESR, 0);
                 apic_read(APIC_ESR);
         }
 
@@ -639,13 +636,13 @@ wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
         /*
          * Turn INIT on target chip
          */
-        apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));
+        apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));
 
         /*
          * Send IPI
          */
-        apic_write_around(APIC_ICR, APIC_INT_LEVELTRIG | APIC_INT_ASSERT
-                                | APIC_DM_INIT);
+        apic_write(APIC_ICR,
+                   APIC_INT_LEVELTRIG | APIC_INT_ASSERT | APIC_DM_INIT);
 
         Dprintk("Waiting for send to finish...\n");
         send_status = safe_apic_wait_icr_idle();
@@ -655,10 +652,10 @@ wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
         Dprintk("Deasserting INIT.\n");
 
         /* Target chip */
-        apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));
+        apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));
 
         /* Send IPI */
-        apic_write_around(APIC_ICR, APIC_INT_LEVELTRIG | APIC_DM_INIT);
+        apic_write(APIC_ICR, APIC_INT_LEVELTRIG | APIC_DM_INIT);
 
         Dprintk("Waiting for send to finish...\n");
         send_status = safe_apic_wait_icr_idle();
@@ -689,12 +686,10 @@ wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
          */
         Dprintk("#startup loops: %d.\n", num_starts);
 
-        maxlvt = lapic_get_maxlvt();
-
         for (j = 1; j <= num_starts; j++) {
                 Dprintk("Sending STARTUP #%d.\n", j);
-                apic_read_around(APIC_SPIV);
-                apic_write(APIC_ESR, 0);
+                if (maxlvt > 3)         /* Due to the Pentium erratum 3AP.  */
+                        apic_write(APIC_ESR, 0);
                 apic_read(APIC_ESR);
                 Dprintk("After apic_write.\n");
 
@@ -703,12 +698,11 @@ wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
                  */
 
                 /* Target chip */
-                apic_write_around(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));
+                apic_write(APIC_ICR2, SET_APIC_DEST_FIELD(phys_apicid));
 
                 /* Boot on the stack */
                 /* Kick the second */
-                apic_write_around(APIC_ICR, APIC_DM_STARTUP
-                                        | (start_eip >> 12));
+                apic_write(APIC_ICR, APIC_DM_STARTUP | (start_eip >> 12));
 
                 /*
                  * Give the other CPU some time to accept the IPI.
@@ -724,13 +718,8 @@ wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
                  * Give the other CPU some time to accept the IPI.
                  */
                 udelay(200);
-                /*
-                 * Due to the Pentium erratum 3AP.
-                 */
-                if (maxlvt > 3) {
-                        apic_read_around(APIC_SPIV);
+                if (maxlvt > 3)         /* Due to the Pentium erratum 3AP.  */
                         apic_write(APIC_ESR, 0);
-                }
                 accept_status = (apic_read(APIC_ESR) & 0xEF);
                 if (send_status || accept_status)
                         break;