powerpc: Rework context management for CPUs with no hash table

This reworks the context management code used by 4xx,8xx and freescale BookE. It adds support for SMP by implementing a concept of stale context map to lazily flush the TLB on processors where a context may have been invalidated. This also contains the ground work for generalizing such lazy TLB flushing by just picking up a new PID and marking the old one stale. This will be implemented later.

This is a first implementation that uses a global spinlock.

Ideally, we should try to get at least the fast path (context ID already assigned) lockless or limited to a per context lock, but for now this will do.

I tried to keep the UP case reasonably simple to avoid adding too much overhead to 8xx which does a lot of context stealing since it effectively has only 16 PIDs available.

---

 arch/powerpc/include/asm/mmu-40x.h       |    5 
 arch/powerpc/include/asm/mmu-44x.h       |    5 
 arch/powerpc/include/asm/mmu-fsl-booke.h |    5 
 arch/powerpc/mm/mmu_context_nohash.c     |  258 ++++++++++++++++++++++++-------
 4 files changed, 217 insertions(+), 56 deletions(-)

@@ -54,8 +54,9 @@
 #ifndef __ASSEMBLY__
 
 typedef struct {
-	unsigned long id;
-	unsigned long vdso_base;
+	unsigned short	id;
+	unsigned short	active;
+	unsigned long	vdso_base;
 } mm_context_t;
 
 #endif /* !__ASSEMBLY__ */

Index: linux-work/arch/powerpc/include/asm/mmu-44x.h
===================================================================
@@ -56,8 +56,9 @@
 extern unsigned int tlb_44x_hwater;
 
 typedef struct {
-	unsigned long id;
-	unsigned long vdso_base;
+	unsigned short	id;
+	unsigned short	active;
+	unsigned long	vdso_base;
 } mm_context_t;
 
 #endif /* !__ASSEMBLY__ */

Index: linux-work/arch/powerpc/include/asm/mmu-fsl-booke.h
===================================================================
@@ -74,8 +74,9 @@
 #ifndef __ASSEMBLY__
 
 typedef struct {
-	unsigned long id;
-	unsigned long vdso_base;
+	unsigned short	id;
+	unsigned short	active;
+	unsigned long	vdso_base;
 } mm_context_t;
 #endif /* !__ASSEMBLY__ */
 

Hi Ben,

               ^

Cheers,
Stephen Rothwell                    [email protected]
http://www.canb.auug.org.au/~sfr/

Bah, leave me some surprises for Kumar for when he tests on actual SMP hardware :-)

Cheers,
Ben.