powerpc/32s: Don't use SPRN_SPRG_PGDIR in hash_page

SPRN_SPRG_PGDIR is there mainly to speedup SW TLB miss handlers
for powerpc 603.

We need to free SPRN_SPRG2 to reduce the mess with CONFIG_VMAP_STACK.

In hash_page(), reading PGDIR from thread_struct will be in the noise
performance wise.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/4adca19b7120cdf619956768ed09e74fc6a558f3.1606285014.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/mm/book3s32/hash_low.S b/arch/powerpc/mm/book3s32/hash_low.S
index 48415c8..aca353d 100644 (file)
--- a/arch/powerpc/mm/book3s32/hash_low.S
+++ b/arch/powerpc/mm/book3s32/hash_low.S
@@ -65,13 +65,14 @@ _GLOBAL(hash_page)
        /* Get PTE (linux-style) and check access */
        lis     r0, TASK_SIZE@h         /* check if kernel address */
        cmplw   0,r4,r0
+       mfspr   r8,SPRN_SPRG_THREAD     /* current task's THREAD (phys) */
        ori     r3,r3,_PAGE_USER|_PAGE_PRESENT /* test low addresses as user */
-       mfspr   r5, SPRN_SPRG_PGDIR     /* phys page-table root */
+       lwz     r5,PGDIR(r8)            /* virt page-table root */
        blt+    112f                    /* assume user more likely */
-       lis     r5, (swapper_pg_dir - PAGE_OFFSET)@ha   /* if kernel address, use */
-       addi    r5 ,r5 ,(swapper_pg_dir - PAGE_OFFSET)@l        /* kernel page table */
+       lis     r5,swapper_pg_dir@ha    /* if kernel address, use */
+       addi    r5,r5,swapper_pg_dir@l  /* kernel page table */
        rlwimi  r3,r9,32-12,29,29       /* MSR_PR -> _PAGE_USER */
-112:
+112:   tophys(r5, r5)
 #ifndef CONFIG_PTE_64BIT
        rlwimi  r5,r4,12,20,29          /* insert top 10 bits of address */
        lwz     r8,0(r5)                /* get pmd entry */