avr32: Cover the kernel page tables in the user PGDs

Expand the per-process PGDs so that they cover the kernel virtual
memory area as well. This simplifies the TLB miss handler fastpath
since it doesn't have to check for kernel addresses anymore.

If a TLB miss happens on a kernel address and a second-level page
table can't be found, we check swapper_pg_dir and copy the PGD entry
into the user PGD if it can be found there.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S
index 3cdd7071f35e131379e4b1d14adbb15e089d3af6..2b398cae110c839fc5b3c3be3d9d7a48fcf3a2ec 100644 (file)
--- a/arch/avr32/kernel/entry-avr32b.S
+++ b/arch/avr32/kernel/entry-avr32b.S
@@ -98,10 +98,6 @@ tlb_miss_common:
        mfsr    r0, SYSREG_TLBEAR
        mfsr    r1, SYSREG_PTBR
 
-       /* Is it the vmalloc space? */
-       bld     r0, 31
-       brcs    handle_vmalloc_miss
-
        /*
         * First level lookup: The PGD contains virtual pointers to
         * the second-level page tables, but they may be NULL if not
@@ -143,15 +139,13 @@ pgtbl_lookup:
        tlbmiss_restore
        rete
 
-handle_vmalloc_miss:
-       /* Simply do the lookup in init's page table */
-       mov     r1, lo(swapper_pg_dir)
-       orh     r1, hi(swapper_pg_dir)
-       rjmp    pgtbl_lookup
-
        /* The slow path of the TLB miss handler */
        .align  2
 page_table_not_present:
+       /* Do we need to synchronize with swapper_pg_dir? */
+       bld     r0, 31
+       brcs    sync_with_swapper_pg_dir
+
 page_not_present:
        tlbmiss_restore
        sub     sp, 4
@@ -162,6 +156,34 @@ page_not_present:
        rcall   do_page_fault
        rjmp    ret_from_exception
 
+       .align  2
+sync_with_swapper_pg_dir:
+       /*
+        * If swapper_pg_dir contains a non-NULL second-level page
+        * table pointer, copy it into the current PGD. If not, we
+        * must handle it as a full-blown page fault.
+        *
+        * Jumping back to pgtbl_lookup causes an unnecessary lookup,
+        * but it is guaranteed to be a cache hit, it won't happen
+        * very often, and we absolutely do not want to sacrifice any
+        * performance in the fast path in order to improve this.
+        */
+       mov     r1, lo(swapper_pg_dir)
+       orh     r1, hi(swapper_pg_dir)
+       ld.w    r3, r1[r2 << 2]
+       cp.w    r3, 0
+       breq    page_not_present
+       mfsr    r1, SYSREG_PTBR
+       st.w    r1[r2 << 2], r3
+       rjmp    pgtbl_lookup
+
+       /*
+        * We currently have two bytes left at this point until we
+        * crash into the system call handler...
+        *
+        * Don't worry, the assembler will let us know.
+        */
+
 
        /* ---                    System Call                    --- */
 

diff --git a/include/asm-avr32/pgalloc.h b/include/asm-avr32/pgalloc.h
index 5b768fc2388e1e298ebdccc3074534804f8a49a4..e9636d1f383fa8e77dd3130a5b4a750ddd04636c 100644 (file)
--- a/include/asm-avr32/pgalloc.h
+++ b/include/asm-avr32/pgalloc.h
@@ -9,8 +9,6 @@
 #define __ASM_AVR32_PGALLOC_H
 
 #include <linux/mm.h>
-#include <linux/sched.h>
-#include <linux/slab.h>
 
 static inline void pmd_populate_kernel(struct mm_struct *mm,
                                       pmd_t *pmd, pte_t *pte)
@@ -30,12 +28,20 @@ static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd,
  */
 static inline pgd_t *pgd_alloc(struct mm_struct *mm)
 {
-       return kcalloc(USER_PTRS_PER_PGD, sizeof(pgd_t), GFP_KERNEL);
+       pgd_t *pgd;
+
+       pgd = (pgd_t *)get_zeroed_page(GFP_KERNEL | __GFP_REPEAT);
+       if (likely(pgd))
+               memcpy(pgd + USER_PTRS_PER_PGD,
+                       swapper_pg_dir + USER_PTRS_PER_PGD,
+                       (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
+
+       return pgd;
 }
 
 static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 {
-       kfree(pgd);
+       free_page((unsigned long)pgd);
 }
 
 static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,