[POWERPC] Implement SLB shadow buffer

This adds a shadow buffer for the SLBs and regsiters it with PHYP.
Only the bolted SLB entries (top 3) are shadowed.

The SLB shadow buffer tells the hypervisor what the kernel needs to
have in the SLB for the kernel to be able to function.  The hypervisor
can use this information to speed up partition context switches.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 29 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index ac0631958b20..2ef7ea860379 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -135,11 +135,13 @@ int main(void)
         DEFINE(PACA_STARTPURR, offsetof(struct paca_struct, startpurr));
         DEFINE(PACA_USER_TIME, offsetof(struct paca_struct, user_time));
         DEFINE(PACA_SYSTEM_TIME, offsetof(struct paca_struct, system_time));
+        DEFINE(PACA_SLBSHADOWPTR, offsetof(struct paca_struct, slb_shadow_ptr));
 
         DEFINE(LPPACASRR0, offsetof(struct lppaca, saved_srr0));
         DEFINE(LPPACASRR1, offsetof(struct lppaca, saved_srr1));
         DEFINE(LPPACAANYINT, offsetof(struct lppaca, int_dword.any_int));
         DEFINE(LPPACADECRINT, offsetof(struct lppaca, int_dword.fields.decr_int));
+        DEFINE(SLBSHADOW_SAVEAREA, offsetof(struct slb_shadow, save_area));
 #endif /* CONFIG_PPC64 */
 
         /* RTAS */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 54d9f5cdaab4..5baea498ea64 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -323,6 +323,11 @@ _GLOBAL(ret_from_fork)
  * The code which creates the new task context is in 'copy_thread'
  * in arch/powerpc/kernel/process.c 
  */
+#define SHADOW_SLB_BOLTED_STACK_ESID \
+                (SLBSHADOW_SAVEAREA + 0x10*(SLB_NUM_BOLTED-1))
+#define SHADOW_SLB_BOLTED_STACK_VSID \
+                (SLBSHADOW_SAVEAREA + 0x10*(SLB_NUM_BOLTED-1) + 8)
+
         .align  7
 _GLOBAL(_switch)
         mflr    r0
@@ -375,6 +380,14 @@ 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
+
+        /* Update the last bolted SLB */
+        ld      r9,PACA_SLBSHADOWPTR(r13)
+        li      r12,0
+        std     r12,SHADOW_SLB_BOLTED_STACK_ESID(r9) /* Clear ESID */
+        std     r7,SHADOW_SLB_BOLTED_STACK_VSID(r9)  /* Save VSID */
+        std     r0,SHADOW_SLB_BOLTED_STACK_ESID(r9)  /* Save ESID */
+
         slbie   r6
         slbie   r6              /* Workaround POWER5 < DD2.1 issue */
         slbmte  r7,r0
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index c68741fed14b..55f1a25085cd 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -17,6 +17,7 @@
 #include <asm/lppaca.h>
 #include <asm/iseries/it_lp_reg_save.h>
 #include <asm/paca.h>
+#include <asm/mmu.h>
 
 
 /* This symbol is provided by the linker - let it fill in the paca
@@ -45,6 +46,17 @@ struct lppaca lppaca[] = {
         },
 };
 
+/*
+ * 3 persistent SLBs are registered here.  The buffer will be zero
+ * initially, hence will all be invaild until we actually write them.
+ */
+struct slb_shadow slb_shadow[] __cacheline_aligned = {
+        [0 ... (NR_CPUS-1)] = {
+                .persistent = SLB_NUM_BOLTED,
+                .buffer_length = sizeof(struct slb_shadow),
+        },
+};
+
 /* The Paca is an array with one entry per processor.  Each contains an
  * lppaca, which contains the information shared between the
  * hypervisor and Linux.
@@ -59,7 +71,8 @@ struct lppaca lppaca[] = {
         .lock_token = 0x8000,                                               \
         .paca_index = (number),         /* Paca Index */                    \
         .kernel_toc = (unsigned long)(&__toc_start) + 0x8000UL,             \
-        .hw_cpu_id = 0xffff,
+        .hw_cpu_id = 0xffff,                                                \
+        .slb_shadow_ptr = &slb_shadow[number],
 
 #ifdef CONFIG_PPC_ISERIES
 #define PACA_INIT_ISERIES(number)                                           \