powerpc: Use an alternative feature section in entry_64.S

Use an alternative feature section in _switch. There are three cases
handled here, either we don't have an SLB, in which case we jump over the
entire code section, or if we do we either do or don't have 1TB segments.

Boot tested on Power3, Power5 and Power5+.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index c0db5b7..6ca3044 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -383,16 +383,16 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 
        ld      r8,KSP(r4)      /* new stack pointer */
 BEGIN_FTR_SECTION
-       b       2f
-END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
-BEGIN_FTR_SECTION
+  BEGIN_FTR_SECTION_NESTED(95)
        clrrdi  r6,r8,28        /* get its ESID */
        clrrdi  r9,r1,28        /* get current sp ESID */
-END_FTR_SECTION_IFCLR(CPU_FTR_1T_SEGMENT)
-BEGIN_FTR_SECTION
+  FTR_SECTION_ELSE_NESTED(95)
        clrrdi  r6,r8,40        /* get its 1T ESID */
        clrrdi  r9,r1,40        /* get current sp 1T ESID */
-END_FTR_SECTION_IFSET(CPU_FTR_1T_SEGMENT)
+  ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_1T_SEGMENT, 95)
+FTR_SECTION_ELSE
+       b       2f
+ALT_FTR_SECTION_END_IFSET(CPU_FTR_SLB)
        clrldi. r0,r6,2         /* is new ESID c00000000? */
        cmpd    cr1,r6,r9       /* or is new ESID the same as current ESID? */
        cror    eq,4*cr1+eq,eq