[POWERPC] Use 1TB segments

This makes the kernel use 1TB segments for all kernel mappings and for
user addresses of 1TB and above, on machines which support them
(currently POWER5+, POWER6 and PA6T).

We detect that the machine supports 1TB segments by looking at the
ibm,processor-segment-sizes property in the device tree.

We don't currently use 1TB segments for user addresses < 1T, since
that would effectively prevent 32-bit processes from using huge pages
unless we also had a way to revert to using 256MB segments.  That
would be possible but would involve extra complications (such as
keeping track of which segment size was used when HPTEs were inserted)
and is not addressed here.

Parts of this patch were originally written by Ben Herrenschmidt.

Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 21 insertions, 4 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index fbbd3f6f0064..0ec134034899 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -373,8 +373,16 @@ 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
         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
+        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)
         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
@@ -384,6 +392,11 @@ BEGIN_FTR_SECTION
         ld      r7,KSP_VSID(r4) /* Get new stack's VSID */
         oris    r0,r6,(SLB_ESID_V)@h
         ori     r0,r0,(SLB_NUM_BOLTED-1)@l
+BEGIN_FTR_SECTION
+        li      r9,MMU_SEGSIZE_1T       /* insert B field */
+        oris    r6,r6,(MMU_SEGSIZE_1T << SLBIE_SSIZE_SHIFT)@h
+        rldimi  r7,r9,SLB_VSID_SSIZE_SHIFT,0
+END_FTR_SECTION_IFSET(CPU_FTR_1T_SEGMENT)
 
         /* Update the last bolted SLB.  No write barriers are needed
          * here, provided we only update the current CPU's SLB shadow
@@ -401,7 +414,6 @@ BEGIN_FTR_SECTION
         isync
 
 2:
-END_FTR_SECTION_IFSET(CPU_FTR_SLB)
         clrrdi  r7,r8,THREAD_SHIFT      /* base of new stack */
         /* Note: this uses SWITCH_FRAME_SIZE rather than INT_FRAME_SIZE
            because we don't need to leave the 288-byte ABI gap at the
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 22ac245bd59a..97c5857faf00 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -935,7 +935,7 @@ _GLOBAL(do_stab_bolted)
 
         /* Calculate VSID */
         /* This is a kernel address, so protovsid = ESID */
-        ASM_VSID_SCRAMBLE(r11, r9)
+        ASM_VSID_SCRAMBLE(r11, r9, 256M)
         rldic   r9,r11,12,16    /* r9 = vsid << 12 */
 
         /* Search the primary group for a free entry */
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 15998b57767c..7949c203cb89 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -564,10 +564,15 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 
 #ifdef CONFIG_PPC64
         if (cpu_has_feature(CPU_FTR_SLB)) {
-                unsigned long sp_vsid = get_kernel_vsid(sp);
+                unsigned long sp_vsid;
                 unsigned long llp = mmu_psize_defs[mmu_linear_psize].sllp;
 
-                sp_vsid <<= SLB_VSID_SHIFT;
+                if (cpu_has_feature(CPU_FTR_1T_SEGMENT))
+                        sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_1T)
+                                << SLB_VSID_SHIFT_1T;
+                else
+                        sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_256M)
+                                << SLB_VSID_SHIFT;
                 sp_vsid |= SLB_VSID_KERNEL | llp;
                 p->thread.ksp_vsid = sp_vsid;
         }