[PATCH] x86: SMP alternatives

Implement SMP alternatives, i.e.  switching at runtime between different
code versions for UP and SMP.  The code can patch both SMP->UP and UP->SMP.
The UP->SMP case is useful for CPU hotplug.

With CONFIG_CPU_HOTPLUG enabled the code switches to UP at boot time and
when the number of CPUs goes down to 1, and switches to SMP when the number
of CPUs goes up to 2.

Without CONFIG_CPU_HOTPLUG or on non-SMP-capable systems the code is
patched once at boot time (if needed) and the tables are released
afterwards.

The changes in detail:

  * The current alternatives bits are moved to a separate file,
    the SMP alternatives code is added there.

  * The patch adds some new elf sections to the kernel:
    .smp_altinstructions
	like .altinstructions, also contains a list
	of alt_instr structs.
    .smp_altinstr_replacement
	like .altinstr_replacement, but also has some space to
	save original instruction before replaving it.
    .smp_locks
	list of pointers to lock prefixes which can be nop'ed
	out on UP.
    The first two are used to replace more complex instruction
    sequences such as spinlocks and semaphores.  It would be possible
    to deal with the lock prefixes with that as well, but by handling
    them as special case the table sizes become much smaller.

 * The sections are page-aligned and padded up to page size, so they
   can be free if they are not needed.

 * Splitted the code to release init pages to a separate function and
   use it to release the elf sections if they are unused.

Signed-off-by: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 0 insertions, 95 deletions

diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
index ab62a9f..5f58f8c 100644
--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c
@@ -1377,101 +1377,6 @@ static void __init register_memory(void)
 		pci_mem_start, gapstart, gapsize);
 }
 
-/* Use inline assembly to define this because the nops are defined 
-   as inline assembly strings in the include files and we cannot 
-   get them easily into strings. */
-asm("\t.data\nintelnops: " 
-    GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6
-    GENERIC_NOP7 GENERIC_NOP8); 
-asm("\t.data\nk8nops: " 
-    K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6
-    K8_NOP7 K8_NOP8); 
-asm("\t.data\nk7nops: " 
-    K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6
-    K7_NOP7 K7_NOP8); 
-    
-extern unsigned char intelnops[], k8nops[], k7nops[];
-static unsigned char *intel_nops[ASM_NOP_MAX+1] = { 
-     NULL,
-     intelnops,
-     intelnops + 1,
-     intelnops + 1 + 2,
-     intelnops + 1 + 2 + 3,
-     intelnops + 1 + 2 + 3 + 4,
-     intelnops + 1 + 2 + 3 + 4 + 5,
-     intelnops + 1 + 2 + 3 + 4 + 5 + 6,
-     intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
-}; 
-static unsigned char *k8_nops[ASM_NOP_MAX+1] = { 
-     NULL,
-     k8nops,
-     k8nops + 1,
-     k8nops + 1 + 2,
-     k8nops + 1 + 2 + 3,
-     k8nops + 1 + 2 + 3 + 4,
-     k8nops + 1 + 2 + 3 + 4 + 5,
-     k8nops + 1 + 2 + 3 + 4 + 5 + 6,
-     k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
-}; 
-static unsigned char *k7_nops[ASM_NOP_MAX+1] = { 
-     NULL,
-     k7nops,
-     k7nops + 1,
-     k7nops + 1 + 2,
-     k7nops + 1 + 2 + 3,
-     k7nops + 1 + 2 + 3 + 4,
-     k7nops + 1 + 2 + 3 + 4 + 5,
-     k7nops + 1 + 2 + 3 + 4 + 5 + 6,
-     k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
-}; 
-static struct nop { 
-     int cpuid; 
-     unsigned char **noptable; 
-} noptypes[] = { 
-     { X86_FEATURE_K8, k8_nops }, 
-     { X86_FEATURE_K7, k7_nops }, 
-     { -1, NULL }
-}; 
-
-/* Replace instructions with better alternatives for this CPU type.
-
-   This runs before SMP is initialized to avoid SMP problems with
-   self modifying code. This implies that assymetric systems where
-   APs have less capabilities than the boot processor are not handled. 
-   Tough. Make sure you disable such features by hand. */ 
-void apply_alternatives(void *start, void *end) 
-{ 
-	struct alt_instr *a; 
-	int diff, i, k;
-        unsigned char **noptable = intel_nops; 
-	for (i = 0; noptypes[i].cpuid >= 0; i++) { 
-		if (boot_cpu_has(noptypes[i].cpuid)) { 
-			noptable = noptypes[i].noptable;
-			break;
-		}
-	} 
-	for (a = start; (void *)a < end; a++) { 
-		if (!boot_cpu_has(a->cpuid))
-			continue;
-		BUG_ON(a->replacementlen > a->instrlen); 
-		memcpy(a->instr, a->replacement, a->replacementlen); 
-		diff = a->instrlen - a->replacementlen; 
-		/* Pad the rest with nops */
-		for (i = a->replacementlen; diff > 0; diff -= k, i += k) {
-			k = diff;
-			if (k > ASM_NOP_MAX)
-				k = ASM_NOP_MAX;
-			memcpy(a->instr + i, noptable[k], k); 
-		} 
-	}
-} 
-
-void __init alternative_instructions(void)
-{
-	extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
-	apply_alternatives(__alt_instructions, __alt_instructions_end);
-}
-
 static char * __init machine_specific_memory_setup(void);
 
 #ifdef CONFIG_MCA