powerpc: Use 64k pages without needing cache-inhibited large pages

Some POWER5+ machines can do 64k hardware pages for normal memory but
not for cache-inhibited pages.  This patch lets us use 64k hardware
pages for most user processes on such machines (assuming the kernel
has been configured with CONFIG_PPC_64K_PAGES=y).  User processes
start out using 64k pages and get switched to 4k pages if they use any
non-cacheable mappings.

With this, we use 64k pages for the vmalloc region and 4k pages for
the imalloc region.  If anything creates a non-cacheable mapping in
the vmalloc region, the vmalloc region will get switched to 4k pages.
I don't know of any driver other than the DRM that would do this,
though, and these machines don't have AGP.

When a region gets switched from 64k pages to 4k pages, we do not have
to clear out all the 64k HPTEs from the hash table immediately.  We
use the _PAGE_COMBO bit in the Linux PTE to indicate whether the page
was hashed in as a 64k page or a set of 4k pages.  If hash_page is
trying to insert a 4k page for a Linux PTE and it sees that it has
already been inserted as a 64k page, it first invalidates the 64k HPTE
before inserting the 4k HPTE.  The hash invalidation routines also use
the _PAGE_COMBO bit, to determine whether to look for a 64k HPTE or a
set of 4k HPTEs to remove.  With those two changes, we can tolerate a
mix of 4k and 64k HPTEs in the hash table, and they will all get
removed when the address space is torn down.

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

8 files changed, 140 insertions, 31 deletions

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index aa0486d552a3..ff2940548929 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -122,6 +122,8 @@ int main(void)
         DEFINE(PACASLBCACHE, offsetof(struct paca_struct, slb_cache));
         DEFINE(PACASLBCACHEPTR, offsetof(struct paca_struct, slb_cache_ptr));
         DEFINE(PACACONTEXTID, offsetof(struct paca_struct, context.id));
+        DEFINE(PACACONTEXTSLLP, offsetof(struct paca_struct, context.sllp));
+        DEFINE(PACAVMALLOCSLLP, offsetof(struct paca_struct, vmalloc_sllp));
 #ifdef CONFIG_HUGETLB_PAGE
         DEFINE(PACALOWHTLBAREAS, offsetof(struct paca_struct, context.low_htlb_areas));
         DEFINE(PACAHIGHHTLBAREAS, offsetof(struct paca_struct, context.high_htlb_areas));
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 969f4abcc0be..d77d24a89b39 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -948,7 +948,10 @@ static struct ibm_pa_feature {
         {CPU_FTR_CTRL, 0,               0, 3, 0},
         {CPU_FTR_NOEXECUTE, 0,          0, 6, 0},
         {CPU_FTR_NODSISRALIGN, 0,       1, 1, 1},
+#if 0
+        /* put this back once we know how to test if firmware does 64k IO */
         {CPU_FTR_CI_LARGE_PAGE, 0,      1, 2, 0},
+#endif
 };
 
 static void __init check_cpu_pa_features(unsigned long node)
diff --git a/arch/powerpc/mm/hash_low_64.S b/arch/powerpc/mm/hash_low_64.S
index 106fba391987..52e914238959 100644
--- a/arch/powerpc/mm/hash_low_64.S
+++ b/arch/powerpc/mm/hash_low_64.S
@@ -369,6 +369,7 @@ _GLOBAL(__hash_page_4K)
         rlwinm  r30,r4,32-9+7,31-7,31-7 /* _PAGE_RW -> _PAGE_DIRTY */
         or      r30,r30,r31
         ori     r30,r30,_PAGE_BUSY | _PAGE_ACCESSED | _PAGE_HASHPTE
+        oris    r30,r30,_PAGE_COMBO@h
         /* Write the linux PTE atomically (setting busy) */
         stdcx.  r30,0,r6
         bne-    1b
@@ -428,6 +429,14 @@ END_FTR_SECTION(CPU_FTR_NOEXECUTE|CPU_FTR_COHERENT_ICACHE, CPU_FTR_NOEXECUTE)
         andi.   r0,r31,_PAGE_HASHPTE
         li      r26,0                   /* Default hidx */
         beq     htab_insert_pte
+
+        /*
+         * Check if the pte was already inserted into the hash table
+         * as a 64k HW page, and invalidate the 64k HPTE if so.
+         */
+        andis.  r0,r31,_PAGE_COMBO@h
+        beq     htab_inval_old_hpte
+
         ld      r6,STK_PARM(r6)(r1)
         ori     r26,r6,0x8000           /* Load the hidx mask */
         ld      r26,0(r26)
@@ -498,6 +507,19 @@ _GLOBAL(htab_call_hpte_remove)
         /* Try all again */
         b       htab_insert_pte
 
+        /*
+         * Call out to C code to invalidate an 64k HW HPTE that is
+         * useless now that the segment has been switched to 4k pages.
+         */
+htab_inval_old_hpte:
+        mr      r3,r29                  /* virtual addr */
+        mr      r4,r31                  /* PTE.pte */
+        li      r5,0                    /* PTE.hidx */
+        li      r6,MMU_PAGE_64K         /* psize */
+        ld      r7,STK_PARM(r8)(r1)     /* local */
+        bl      .flush_hash_page
+        b       htab_insert_pte
+        
 htab_bail_ok:
         li      r3,0
         b       htab_bail
@@ -638,6 +660,12 @@ _GLOBAL(__hash_page_64K)
          * is changing this PTE anyway and might hash it.
          */
         bne-    ht64_bail_ok
+BEGIN_FTR_SECTION
+        /* Check if PTE has the cache-inhibit bit set */
+        andi.   r0,r31,_PAGE_NO_CACHE
+        /* If so, bail out and refault as a 4k page */
+        bne-    ht64_bail_ok
+END_FTR_SECTION_IFCLR(CPU_FTR_CI_LARGE_PAGE)
         /* Prepare new PTE value (turn access RW into DIRTY, then
          * add BUSY,HASHPTE and ACCESSED)
          */
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index b43ed92ef471..d03fd2b4445e 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -92,10 +92,15 @@ unsigned long htab_size_bytes;
 unsigned long htab_hash_mask;
 int mmu_linear_psize = MMU_PAGE_4K;
 int mmu_virtual_psize = MMU_PAGE_4K;
+int mmu_vmalloc_psize = MMU_PAGE_4K;
+int mmu_io_psize = MMU_PAGE_4K;
 #ifdef CONFIG_HUGETLB_PAGE
 int mmu_huge_psize = MMU_PAGE_16M;
 unsigned int HPAGE_SHIFT;
 #endif
+#ifdef CONFIG_PPC_64K_PAGES
+int mmu_ci_restrictions;
+#endif
 
 /* There are definitions of page sizes arrays to be used when none
  * is provided by the firmware.
@@ -308,20 +313,31 @@ static void __init htab_init_page_sizes(void)
         else if (mmu_psize_defs[MMU_PAGE_1M].shift)
                 mmu_linear_psize = MMU_PAGE_1M;
 
+#ifdef CONFIG_PPC_64K_PAGES
         /*
          * Pick a size for the ordinary pages. Default is 4K, we support
-         * 64K if cache inhibited large pages are supported by the
-         * processor
+         * 64K for user mappings and vmalloc if supported by the processor.
+         * We only use 64k for ioremap if the processor
+         * (and firmware) support cache-inhibited large pages.
+         * If not, we use 4k and set mmu_ci_restrictions so that
+         * hash_page knows to switch processes that use cache-inhibited
+         * mappings to 4k pages.
          */
-#ifdef CONFIG_PPC_64K_PAGES
-        if (mmu_psize_defs[MMU_PAGE_64K].shift &&
-            cpu_has_feature(CPU_FTR_CI_LARGE_PAGE))
+        if (mmu_psize_defs[MMU_PAGE_64K].shift) {
                 mmu_virtual_psize = MMU_PAGE_64K;
+                mmu_vmalloc_psize = MMU_PAGE_64K;
+                if (cpu_has_feature(CPU_FTR_CI_LARGE_PAGE))
+                        mmu_io_psize = MMU_PAGE_64K;
+                else
+                        mmu_ci_restrictions = 1;
+        }
 #endif
 
-        printk(KERN_DEBUG "Page orders: linear mapping = %d, others = %d\n",
+        printk(KERN_DEBUG "Page orders: linear mapping = %d, "
+               "virtual = %d, io = %d\n",
                mmu_psize_defs[mmu_linear_psize].shift,
-               mmu_psize_defs[mmu_virtual_psize].shift);
+               mmu_psize_defs[mmu_virtual_psize].shift,
+               mmu_psize_defs[mmu_io_psize].shift);
 
 #ifdef CONFIG_HUGETLB_PAGE
         /* Init large page size. Currently, we pick 16M or 1M depending
@@ -556,6 +572,7 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
         pte_t *ptep;
         cpumask_t tmp;
         int rc, user_region = 0, local = 0;
+        int psize;
 
         DBG_LOW("hash_page(ea=%016lx, access=%lx, trap=%lx\n",
                 ea, access, trap);
@@ -575,10 +592,15 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
                         return 1;
                 }
                 vsid = get_vsid(mm->context.id, ea);
+                psize = mm->context.user_psize;
                 break;
         case VMALLOC_REGION_ID:
                 mm = &init_mm;
                 vsid = get_kernel_vsid(ea);
+                if (ea < VMALLOC_END)
+                        psize = mmu_vmalloc_psize;
+                else
+                        psize = mmu_io_psize;
                 break;
         default:
                 /* Not a valid range
@@ -629,7 +651,40 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
 #ifndef CONFIG_PPC_64K_PAGES
         rc = __hash_page_4K(ea, access, vsid, ptep, trap, local);
 #else
-        if (mmu_virtual_psize == MMU_PAGE_64K)
+        if (mmu_ci_restrictions) {
+                /* If this PTE is non-cacheable, switch to 4k */
+                if (psize == MMU_PAGE_64K &&
+                    (pte_val(*ptep) & _PAGE_NO_CACHE)) {
+                        if (user_region) {
+                                psize = MMU_PAGE_4K;
+                                mm->context.user_psize = MMU_PAGE_4K;
+                                mm->context.sllp = SLB_VSID_USER |
+                                        mmu_psize_defs[MMU_PAGE_4K].sllp;
+                        } else if (ea < VMALLOC_END) {
+                                /*
+                                 * some driver did a non-cacheable mapping
+                                 * in vmalloc space, so switch vmalloc
+                                 * to 4k pages
+                                 */
+                                printk(KERN_ALERT "Reducing vmalloc segment "
+                                       "to 4kB pages because of "
+                                       "non-cacheable mapping\n");
+                                psize = mmu_vmalloc_psize = MMU_PAGE_4K;
+                        }
+                }
+                if (user_region) {
+                        if (psize != get_paca()->context.user_psize) {
+                                get_paca()->context = mm->context;
+                                slb_flush_and_rebolt();
+                        }
+                } else if (get_paca()->vmalloc_sllp !=
+                           mmu_psize_defs[mmu_vmalloc_psize].sllp) {
+                        get_paca()->vmalloc_sllp =
+                                mmu_psize_defs[mmu_vmalloc_psize].sllp;
+                        slb_flush_and_rebolt();
+                }
+        }
+        if (psize == MMU_PAGE_64K)
                 rc = __hash_page_64K(ea, access, vsid, ptep, trap, local);
         else
                 rc = __hash_page_4K(ea, access, vsid, ptep, trap, local);
@@ -681,7 +736,18 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 #ifndef CONFIG_PPC_64K_PAGES
         __hash_page_4K(ea, access, vsid, ptep, trap, local);
 #else
-        if (mmu_virtual_psize == MMU_PAGE_64K)
+        if (mmu_ci_restrictions) {
+                /* If this PTE is non-cacheable, switch to 4k */
+                if (mm->context.user_psize == MMU_PAGE_64K &&
+                    (pte_val(*ptep) & _PAGE_NO_CACHE)) {
+                        mm->context.user_psize = MMU_PAGE_4K;
+                        mm->context.sllp = SLB_VSID_USER |
+                                mmu_psize_defs[MMU_PAGE_4K].sllp;
+                        get_paca()->context = mm->context;
+                        slb_flush_and_rebolt();
+                }
+        }
+        if (mm->context.user_psize == MMU_PAGE_64K)
                 __hash_page_64K(ea, access, vsid, ptep, trap, local);
         else
                 __hash_page_4K(ea, access, vsid, ptep, trap, local);
diff --git a/arch/powerpc/mm/mmu_context_64.c b/arch/powerpc/mm/mmu_context_64.c
index 714a84dd8d5d..65d18dca266f 100644
--- a/arch/powerpc/mm/mmu_context_64.c
+++ b/arch/powerpc/mm/mmu_context_64.c
@@ -49,6 +49,9 @@ again:
         }
 
         mm->context.id = index;
+        mm->context.user_psize = mmu_virtual_psize;
+        mm->context.sllp = SLB_VSID_USER |
+                mmu_psize_defs[mmu_virtual_psize].sllp;
 
         return 0;
 }
diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 2cc61736feee..6a8bf6c6000e 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -60,19 +60,19 @@ static inline void create_slbe(unsigned long ea, unsigned long flags,
                      : "memory" );
 }
 
-static void slb_flush_and_rebolt(void)
+void slb_flush_and_rebolt(void)
 {
         /* If you change this make sure you change SLB_NUM_BOLTED
          * appropriately too. */
-        unsigned long linear_llp, virtual_llp, lflags, vflags;
+        unsigned long linear_llp, vmalloc_llp, lflags, vflags;
         unsigned long ksp_esid_data;
 
         WARN_ON(!irqs_disabled());
 
         linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
-        virtual_llp = mmu_psize_defs[mmu_virtual_psize].sllp;
+        vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
         lflags = SLB_VSID_KERNEL | linear_llp;
-        vflags = SLB_VSID_KERNEL | virtual_llp;
+        vflags = SLB_VSID_KERNEL | vmalloc_llp;
 
         ksp_esid_data = mk_esid_data(get_paca()->kstack, 2);
         if ((ksp_esid_data & ESID_MASK) == PAGE_OFFSET)
@@ -164,11 +164,10 @@ static inline void patch_slb_encoding(unsigned int *insn_addr,
 
 void slb_initialize(void)
 {
-        unsigned long linear_llp, virtual_llp;
+        unsigned long linear_llp, vmalloc_llp, io_llp;
         static int slb_encoding_inited;
         extern unsigned int *slb_miss_kernel_load_linear;
-        extern unsigned int *slb_miss_kernel_load_virtual;
-        extern unsigned int *slb_miss_user_load_normal;
+        extern unsigned int *slb_miss_kernel_load_io;
 #ifdef CONFIG_HUGETLB_PAGE
         extern unsigned int *slb_miss_user_load_huge;
         unsigned long huge_llp;
@@ -178,18 +177,19 @@ void slb_initialize(void)
 
         /* Prepare our SLB miss handler based on our page size */
         linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
-        virtual_llp = mmu_psize_defs[mmu_virtual_psize].sllp;
+        io_llp = mmu_psize_defs[mmu_io_psize].sllp;
+        vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
+        get_paca()->vmalloc_sllp = SLB_VSID_KERNEL | vmalloc_llp;
+
         if (!slb_encoding_inited) {
                 slb_encoding_inited = 1;
                 patch_slb_encoding(slb_miss_kernel_load_linear,
                                    SLB_VSID_KERNEL | linear_llp);
-                patch_slb_encoding(slb_miss_kernel_load_virtual,
-                                   SLB_VSID_KERNEL | virtual_llp);
-                patch_slb_encoding(slb_miss_user_load_normal,
-                                   SLB_VSID_USER | virtual_llp);
+                patch_slb_encoding(slb_miss_kernel_load_io,
+                                   SLB_VSID_KERNEL | io_llp);
 
                 DBG("SLB: linear  LLP = %04x\n", linear_llp);
-                DBG("SLB: virtual LLP = %04x\n", virtual_llp);
+                DBG("SLB: io      LLP = %04x\n", io_llp);
 #ifdef CONFIG_HUGETLB_PAGE
                 patch_slb_encoding(slb_miss_user_load_huge,
                                    SLB_VSID_USER | huge_llp);
@@ -204,7 +204,7 @@ void slb_initialize(void)
         unsigned long lflags, vflags;
 
         lflags = SLB_VSID_KERNEL | linear_llp;
-        vflags = SLB_VSID_KERNEL | virtual_llp;
+        vflags = SLB_VSID_KERNEL | vmalloc_llp;
 
         /* Invalidate the entire SLB (even slot 0) & all the ERATS */
         asm volatile("isync":::"memory");
@@ -212,7 +212,6 @@ void slb_initialize(void)
         asm volatile("isync; slbia; isync":::"memory");
         create_slbe(PAGE_OFFSET, lflags, 0);
 
-        /* VMALLOC space has 4K pages always for now */
         create_slbe(VMALLOC_START, vflags, 1);
 
         /* We don't bolt the stack for the time being - we're in boot,
diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
index abfaabf667bf..8548dcf8ef8b 100644
--- a/arch/powerpc/mm/slb_low.S
+++ b/arch/powerpc/mm/slb_low.S
@@ -59,10 +59,19 @@ _GLOBAL(slb_miss_kernel_load_linear)
         li      r11,0
         b       slb_finish_load
 
-1:      /* vmalloc/ioremap mapping encoding bits, the "li" instruction below
+1:      /* vmalloc/ioremap mapping encoding bits, the "li" instructions below
          * will be patched by the kernel at boot
          */
-_GLOBAL(slb_miss_kernel_load_virtual)
+BEGIN_FTR_SECTION
+        /* check whether this is in vmalloc or ioremap space */
+        clrldi  r11,r10,48
+        cmpldi  r11,(VMALLOC_SIZE >> 28) - 1
+        bgt     5f
+        lhz     r11,PACAVMALLOCSLLP(r13)
+        b       slb_finish_load
+5:
+END_FTR_SECTION_IFCLR(CPU_FTR_CI_LARGE_PAGE)
+_GLOBAL(slb_miss_kernel_load_io)
         li      r11,0
         b       slb_finish_load
 
@@ -96,9 +105,7 @@ _GLOBAL(slb_miss_user_load_huge)
 1:
 #endif /* CONFIG_HUGETLB_PAGE */
 
-_GLOBAL(slb_miss_user_load_normal)
-        li      r11,0
-
+        lhz     r11,PACACONTEXTSLLP(r13)
 2:
         ld      r9,PACACONTEXTID(r13)
         rldimi  r10,r9,USER_ESID_BITS,0
diff --git a/arch/powerpc/mm/tlb_64.c b/arch/powerpc/mm/tlb_64.c
index f734b11566c2..e7449b068c82 100644
--- a/arch/powerpc/mm/tlb_64.c
+++ b/arch/powerpc/mm/tlb_64.c
@@ -131,7 +131,7 @@ void hpte_update(struct mm_struct *mm, unsigned long addr,
 {
         struct ppc64_tlb_batch *batch = &__get_cpu_var(ppc64_tlb_batch);
         unsigned long vsid;
-        unsigned int psize = mmu_virtual_psize;
+        unsigned int psize;
         int i;
 
         i = batch->index;
@@ -148,7 +148,8 @@ void hpte_update(struct mm_struct *mm, unsigned long addr,
 #else
                 BUG();
 #endif
-        }
+        } else
+                psize = pte_pagesize_index(pte);
 
         /*
          * This can happen when we are in the middle of a TLB batch and