[XTENSA] Add support for cache-aliasing

Add support for processors that have cache-aliasing issues, such as
the Stretch S5000 processor. Cache-aliasing means that the size of
the cache (for one way) is larger than the page size, thus, a page
can end up in several places in cache depending on the virtual to
physical translation. The method used here is to map a user page
temporarily through the auto-refill way 0 and of of the DTLB.
We probably will want to revisit this issue and use a better
approach with kmap/kunmap.

Signed-off-by: Chris Zankel <chris@zankel.net>

5 files changed, 547 insertions, 279 deletions

diff --git a/arch/xtensa/mm/Makefile b/arch/xtensa/mm/Makefile
index a5aed5932d7..10aec22a8f9 100644
--- a/arch/xtensa/mm/Makefile
+++ b/arch/xtensa/mm/Makefile
@@ -5,9 +5,5 @@
 # removes any old dependencies. DON'T put your own dependencies here
 # unless it's something special (ie not a .c file).
 #
-# Note 2! The CFLAGS definition is now in the main makefile...
 
-obj-y	 := init.o fault.o tlb.o misc.o
-obj-m	 :=
-obj-n	 :=
-obj-	 :=
+obj-y	 := init.o fault.o tlb.o misc.o cache.o
diff --git a/arch/xtensa/mm/cache.c b/arch/xtensa/mm/cache.c
new file mode 100644
index 00000000000..9a1fa9478ae
--- /dev/null
+++ b/arch/xtensa/mm/cache.c
@@ -0,0 +1,256 @@
+/*
+ * arch/xtensa/mm/cache.c
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001-2006 Tensilica Inc.
+ *
+ * Chris Zankel	<chris@zankel.net>
+ * Joe Taylor
+ * Marc Gauthier
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/bootmem.h>
+#include <linux/swap.h>
+#include <linux/pagemap.h>
+
+#include <asm/pgtable.h>
+#include <asm/bootparam.h>
+#include <asm/mmu_context.h>
+#include <asm/tlb.h>
+#include <asm/tlbflush.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+
+//#define printd(x...) printk(x)
+#define printd(x...) do { } while(0)
+
+/* 
+ * Note:
+ * The kernel provides one architecture bit PG_arch_1 in the page flags that 
+ * can be used for cache coherency.
+ *
+ * I$-D$ coherency.
+ *
+ * The Xtensa architecture doesn't keep the instruction cache coherent with
+ * the data cache. We use the architecture bit to indicate if the caches
+ * are coherent. The kernel clears this bit whenever a page is added to the
+ * page cache. At that time, the caches might not be in sync. We, therefore,
+ * define this flag as 'clean' if set.
+ *
+ * D-cache aliasing.
+ *
+ * With cache aliasing, we have to always flush the cache when pages are
+ * unmapped (see tlb_start_vma(). So, we use this flag to indicate a dirty
+ * page.
+ * 
+ *
+ *
+ */
+
+#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
+
+/*
+ * Any time the kernel writes to a user page cache page, or it is about to
+ * read from a page cache page this routine is called.
+ *
+ */
+
+void flush_dcache_page(struct page *page)
+{
+	struct address_space *mapping = page_mapping(page);
+
+	/*
+	 * If we have a mapping but the page is not mapped to user-space
+	 * yet, we simply mark this page dirty and defer flushing the 
+	 * caches until update_mmu().
+	 */
+
+	if (mapping && !mapping_mapped(mapping)) {
+		if (!test_bit(PG_arch_1, &page->flags))
+			set_bit(PG_arch_1, &page->flags);
+		return;
+
+	} else {
+
+		unsigned long phys = page_to_phys(page);
+		unsigned long temp = page->index << PAGE_SHIFT;
+		unsigned long alias = !(DCACHE_ALIAS_EQ(temp, phys));
+		unsigned long virt;
+
+		/* 
+		 * Flush the page in kernel space and user space.
+		 * Note that we can omit that step if aliasing is not
+		 * an issue, but we do have to synchronize I$ and D$
+		 * if we have a mapping.
+		 */
+
+		if (!alias && !mapping)
+			return;
+
+		__flush_invalidate_dcache_page((long)page_address(page));
+
+		virt = TLBTEMP_BASE_1 + (temp & DCACHE_ALIAS_MASK);
+
+		if (alias)
+			__flush_invalidate_dcache_page_alias(virt, phys);
+
+		if (mapping)
+			__invalidate_icache_page_alias(virt, phys);
+	}
+
+	/* There shouldn't be an entry in the cache for this page anymore. */
+}
+
+
+/*
+ * For now, flush the whole cache. FIXME??
+ */
+
+void flush_cache_range(struct vm_area_struct* vma, 
+		       unsigned long start, unsigned long end)
+{
+	__flush_invalidate_dcache_all();
+	__invalidate_icache_all();
+}
+
+/* 
+ * Remove any entry in the cache for this page. 
+ *
+ * Note that this function is only called for user pages, so use the
+ * alias versions of the cache flush functions.
+ */
+
+void flush_cache_page(struct vm_area_struct* vma, unsigned long address,
+    		      unsigned long pfn)
+{
+	/* Note that we have to use the 'alias' address to avoid multi-hit */
+
+	unsigned long phys = page_to_phys(pfn_to_page(pfn));
+	unsigned long virt = TLBTEMP_BASE_1 + (address & DCACHE_ALIAS_MASK);
+
+	__flush_invalidate_dcache_page_alias(virt, phys);
+	__invalidate_icache_page_alias(virt, phys);
+}
+
+#endif
+
+void
+update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t pte)
+{
+	unsigned long pfn = pte_pfn(pte);
+	struct page *page;
+
+	if (!pfn_valid(pfn))
+		return;
+
+	page = pfn_to_page(pfn);
+
+	/* Invalidate old entry in TLBs */
+
+	invalidate_itlb_mapping(addr);
+	invalidate_dtlb_mapping(addr);
+
+#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
+
+	if (!PageReserved(page) && test_bit(PG_arch_1, &page->flags)) {
+
+		unsigned long vaddr = TLBTEMP_BASE_1 + (addr & DCACHE_ALIAS_MASK);
+		unsigned long paddr = (unsigned long) page_address(page);
+		unsigned long phys = page_to_phys(page);
+
+		__flush_invalidate_dcache_page(paddr);
+
+		__flush_invalidate_dcache_page_alias(vaddr, phys);
+		__invalidate_icache_page_alias(vaddr, phys);
+
+		clear_bit(PG_arch_1, &page->flags);
+	}
+#else
+	if (!PageReserved(page) && !test_bit(PG_arch_1, &page->flags)
+	    && (vma->vm_flags & VM_EXEC) != 0) {
+		unsigned long vaddr = addr & PAGE_MASK;
+		__flush_dcache_page(vaddr);
+		__invalidate_icache_page(vaddr);
+		set_bit(PG_arch_1, &page->flags);
+	}
+#endif
+}
+
+/*
+ * access_process_vm() has called get_user_pages(), which has done a
+ * flush_dcache_page() on the page.
+ */
+
+#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
+
+void copy_to_user_page(struct vm_area_struct *vma, struct page *page, 
+		unsigned long vaddr, void *dst, const void *src,
+		unsigned long len)
+{
+	unsigned long phys = page_to_phys(page);
+	unsigned long alias = !(DCACHE_ALIAS_EQ(vaddr, phys));
+
+	/* Flush and invalidate user page if aliased. */
+
+	if (alias) {
+		unsigned long temp = TLBTEMP_BASE_1 + (vaddr & DCACHE_ALIAS_MASK);
+		__flush_invalidate_dcache_page_alias(temp, phys);
+	}
+
+	/* Copy data */
+	
+	memcpy(dst, src, len);
+
+	/*
+	 * Flush and invalidate kernel page if aliased and synchronize 
+	 * data and instruction caches for executable pages. 
+	 */
+
+	if (alias) {
+		unsigned long temp = TLBTEMP_BASE_1 + (vaddr & DCACHE_ALIAS_MASK);
+
+		__flush_invalidate_dcache_range((unsigned long) dst, len);
+		if ((vma->vm_flags & VM_EXEC) != 0) {
+			__invalidate_icache_page_alias(temp, phys);
+		}
+
+	} else if ((vma->vm_flags & VM_EXEC) != 0) {
+		__flush_dcache_range((unsigned long)dst,len);
+		__invalidate_icache_range((unsigned long) dst, len);
+	}
+}
+
+extern void copy_from_user_page(struct vm_area_struct *vma, struct page *page,
+		unsigned long vaddr, void *dst, const void *src,
+		unsigned long len)
+{
+	unsigned long phys = page_to_phys(page);
+	unsigned long alias = !(DCACHE_ALIAS_EQ(vaddr, phys));
+
+	/*
+	 * Flush user page if aliased. 
+	 * (Note: a simply flush would be sufficient) 
+	 */
+
+	if (alias) {
+		unsigned long temp = TLBTEMP_BASE_1 + (vaddr & DCACHE_ALIAS_MASK);
+		__flush_invalidate_dcache_page_alias(temp, phys);
+	}
+
+	memcpy(dst, src, len);
+}
+
+#endif
diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
index 16004067add..45d28f217c0 100644
--- a/arch/xtensa/mm/fault.c
+++ b/arch/xtensa/mm/fault.c
@@ -24,6 +24,8 @@
 unsigned long asid_cache = ASID_USER_FIRST;
 void bad_page_fault(struct pt_regs*, unsigned long, int);
 
+#undef DEBUG_PAGE_FAULT
+
 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
@@ -64,7 +66,7 @@ void do_page_fault(struct pt_regs *regs)
 		    exccause == EXCCAUSE_ITLB_MISS ||
 		    exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
 
-#if 0
+#ifdef DEBUG_PAGE_FAULT
 	printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
 	       address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
 #endif
@@ -219,7 +221,7 @@ bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 
 	/* Are we prepared to handle this kernel fault?  */
 	if ((entry = search_exception_tables(regs->pc)) != NULL) {
-#if 1
+#ifdef DEBUG_PAGE_FAULT
 		printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 				current->comm, regs->pc, entry->fixup);
 #endif
diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
index 8415c76f11c..b3086f34a8e 100644
--- a/arch/xtensa/mm/init.c
+++ b/arch/xtensa/mm/init.c
@@ -15,40 +15,24 @@
  * Kevin Chea
  */
 
-#include <linux/init.h>
-#include <linux/signal.h>
-#include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
-#include <linux/string.h>
-#include <linux/types.h>
-#include <linux/ptrace.h>
 #include <linux/bootmem.h>
 #include <linux/swap.h>
+#include <linux/mman.h>
+#include <linux/nodemask.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
 
 #include <asm/pgtable.h>
 #include <asm/bootparam.h>
 #include <asm/mmu_context.h>
 #include <asm/tlb.h>
-#include <asm/tlbflush.h>
 #include <asm/page.h>
 #include <asm/pgalloc.h>
-#include <asm/pgtable.h>
-
 
-#define DEBUG 0
 
 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
-//static DEFINE_SPINLOCK(tlb_lock);
-
-/*
- * This flag is used to indicate that the page was mapped and modified in
- * kernel space, so the cache is probably dirty at that address.
- * If cache aliasing is enabled and the page color mismatches, update_mmu_cache
- * synchronizes the caches if this bit is set.
- */
-
-#define PG_cache_clean PG_arch_1
 
 /* References to section boundaries */
 
@@ -323,228 +307,22 @@ void show_mem(void)
 	printk("%d free pages\n", free);
 }
 
-/* ------------------------------------------------------------------------- */
-
-#if (DCACHE_WAY_SIZE > PAGE_SIZE)
-
-/*
- * With cache aliasing, the page color of the page in kernel space and user
- * space might mismatch. We temporarily map the page to a different virtual
- * address with the same color and clear the page there.
- */
-
-void clear_user_page(void *kaddr, unsigned long vaddr, struct page* page)
-{
-
-  	/*  There shouldn't be any entries for this page. */
-
-	__flush_invalidate_dcache_page_phys(__pa(page_address(page)));
-
-	if (!PAGE_COLOR_EQ(vaddr, kaddr)) {
-		unsigned long v, p;
-
-		/* Temporarily map page to DTLB_WAY_DCACHE_ALIAS0. */
-
-		spin_lock(&tlb_lock);
-
-		p = (unsigned long)pte_val((mk_pte(page,PAGE_KERNEL)));
-		kaddr = (void*)PAGE_COLOR_MAP0(vaddr);
-		v = (unsigned long)kaddr | DTLB_WAY_DCACHE_ALIAS0;
-		__asm__ __volatile__("wdtlb %0,%1; dsync" : :"a" (p), "a" (v));
-
-		clear_page(kaddr);
-
-		spin_unlock(&tlb_lock);
-	} else {
-		clear_page(kaddr);
-	}
-
-	/* We need to make sure that i$ and d$ are coherent. */
-
-	clear_bit(PG_cache_clean, &page->flags);
-}
-
-/*
- * With cache aliasing, we have to make sure that the page color of the page
- * in kernel space matches that of the virtual user address before we read
- * the page. If the page color differ, we create a temporary DTLB entry with
- * the corrent page color and use this 'temporary' address as the source.
- * We then use the same approach as in clear_user_page and copy the data
- * to the kernel space and clear the PG_cache_clean bit to synchronize caches
- * later.
- *
- * Note:
- * Instead of using another 'way' for the temporary DTLB entry, we could
- * probably use the same entry that points to the kernel address (after
- * saving the original value and restoring it when we are done).
- */
+struct kmem_cache *pgtable_cache __read_mostly;
 
-void copy_user_page(void* to, void* from, unsigned long vaddr,
-    		    struct page* to_page)
+static void pgd_ctor(void *addr, struct kmem_cache *cache, unsigned long flags)
 {
-	/* There shouldn't be any entries for the new page. */
-
-	__flush_invalidate_dcache_page_phys(__pa(page_address(to_page)));
-
-	spin_lock(&tlb_lock);
-
-	if (!PAGE_COLOR_EQ(vaddr, from)) {
-		unsigned long v, p, t;
-
-		__asm__ __volatile__ ("pdtlb %1,%2; rdtlb1 %0,%1"
-				      : "=a"(p), "=a"(t) : "a"(from));
-		from = (void*)PAGE_COLOR_MAP0(vaddr);
-		v = (unsigned long)from | DTLB_WAY_DCACHE_ALIAS0;
-		__asm__ __volatile__ ("wdtlb %0,%1; dsync" ::"a" (p), "a" (v));
-	}
-
-	if (!PAGE_COLOR_EQ(vaddr, to)) {
-		unsigned long v, p;
-
-		p = (unsigned long)pte_val((mk_pte(to_page,PAGE_KERNEL)));
-		to = (void*)PAGE_COLOR_MAP1(vaddr);
-		v = (unsigned long)to | DTLB_WAY_DCACHE_ALIAS1;
-		__asm__ __volatile__ ("wdtlb %0,%1; dsync" ::"a" (p), "a" (v));
-	}
-	copy_page(to, from);
-
-	spin_unlock(&tlb_lock);
-
-	/* We need to make sure that i$ and d$ are coherent. */
-
-	clear_bit(PG_cache_clean, &to_page->flags);
-}
-
-
-
-/*
- * Any time the kernel writes to a user page cache page, or it is about to
- * read from a page cache page this routine is called.
- *
- * Note:
- * The kernel currently only provides one architecture bit in the page
- * flags that we use for I$/D$ coherency. Maybe, in future, we can
- * use a sepearte bit for deferred dcache aliasing:
- * If the page is not mapped yet, we only need to set a flag,
- * if mapped, we need to invalidate the page.
- */
-// FIXME: we probably need this for WB caches not only for Page Coloring..
-
-void flush_dcache_page(struct page *page)
-{
-	unsigned long addr = __pa(page_address(page));
-	struct address_space *mapping = page_mapping(page);
-
-	__flush_invalidate_dcache_page_phys(addr);
-
-	if (!test_bit(PG_cache_clean, &page->flags))
-		return;
-
-	/* If this page hasn't been mapped, yet, handle I$/D$ coherency later.*/
-#if 0
-	if (mapping && !mapping_mapped(mapping))
-		clear_bit(PG_cache_clean, &page->flags);
-	else
-#endif
-		__invalidate_icache_page_phys(addr);
-}
-
-void flush_cache_range(struct vm_area_struct* vma, unsigned long s,
-		       unsigned long e)
-{
-	__flush_invalidate_cache_all();
-}
-
-void flush_cache_page(struct vm_area_struct* vma, unsigned long address,
-    		      unsigned long pfn)
-{
-	struct page *page = pfn_to_page(pfn);
-
-	/* Remove any entry for the old mapping. */
-
-	if (current->active_mm == vma->vm_mm) {
-		unsigned long addr = __pa(page_address(page));
-		__flush_invalidate_dcache_page_phys(addr);
-		if ((vma->vm_flags & VM_EXEC) != 0)
-			__invalidate_icache_page_phys(addr);
-	} else {
-		BUG();
-	}
-}
-
-#endif	/* (DCACHE_WAY_SIZE > PAGE_SIZE) */
-
-
-pte_t* pte_alloc_one_kernel (struct mm_struct* mm, unsigned long addr)
-{
-	pte_t* pte = (pte_t*)__get_free_pages(GFP_KERNEL|__GFP_REPEAT, 0);
-	if (likely(pte)) {
-	       	pte_t* ptep = (pte_t*)(pte_val(*pte) + PAGE_OFFSET);
-		int i;
-		for (i = 0; i < 1024; i++, ptep++)
-			pte_clear(mm, addr, ptep);
-	}
-	return pte;
-}
-
-struct page* pte_alloc_one(struct mm_struct *mm, unsigned long addr)
-{
-	struct page *page;
-
-	page = alloc_pages(GFP_KERNEL | __GFP_REPEAT, 0);
-
-	if (likely(page)) {
-		pte_t* ptep = kmap_atomic(page, KM_USER0);
-		int i;
+	pte_t* ptep = (pte_t*)addr;
+	int i;
 
-		for (i = 0; i < 1024; i++, ptep++)
-			pte_clear(mm, addr, ptep);
+	for (i = 0; i < 1024; i++, ptep++)
+		pte_clear(NULL, 0, ptep);
 
-		kunmap_atomic(ptep, KM_USER0);
-	}
-	return page;
 }
 
-
-/*
- * Handle D$/I$ coherency.
- *
- * Note:
- * We only have one architecture bit for the page flags, so we cannot handle
- * cache aliasing, yet.
- */
-
-void
-update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t pte)
+void __init pgtable_cache_init(void)
 {
-	unsigned long pfn = pte_pfn(pte);
-	struct page *page;
-	unsigned long vaddr = addr & PAGE_MASK;
-
-	if (!pfn_valid(pfn))
-		return;
-
-	page = pfn_to_page(pfn);
-
-	invalidate_itlb_mapping(addr);
-	invalidate_dtlb_mapping(addr);
-
-	/* We have a new mapping. Use it. */
-
-	write_dtlb_entry(pte, dtlb_probe(addr));
-
-	/* If the processor can execute from this page, synchronize D$/I$. */
-
-	if ((vma->vm_flags & VM_EXEC) != 0) {
-
-		write_itlb_entry(pte, itlb_probe(addr));
-
-		/* Synchronize caches, if not clean. */
-
-		if (!test_and_set_bit(PG_cache_clean, &page->flags)) {
-			__flush_dcache_page(vaddr);
-			__invalidate_icache_page(vaddr);
-		}
-	}
+	pgtable_cache = kmem_cache_create("pgd",
+			PAGE_SIZE, PAGE_SIZE,
+			SLAB_HWCACHE_ALIGN,
+			pgd_ctor);
 }
-
diff --git a/arch/xtensa/mm/misc.S b/arch/xtensa/mm/misc.S
index ae085332c60..e1f880368e3 100644
--- a/arch/xtensa/mm/misc.S
+++ b/arch/xtensa/mm/misc.S
@@ -7,29 +7,33 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
- * Copyright (C) 2001 - 2005 Tensilica Inc.
+ * Copyright (C) 2001 - 2007 Tensilica Inc.
  *
  * Chris Zankel	<chris@zankel.net>
  */
 
-/* Note: we might want to implement some of the loops as zero-overhead-loops,
- *	 where applicable and if supported by the processor.
- */
 
 #include <linux/linkage.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/asmmacro.h>
 #include <asm/cacheasm.h>
+#include <asm/tlbflush.h>
+
 
-/* clear_page (page) */
+/*
+ * clear_page and clear_user_page are the same for non-cache-aliased configs.
+ *
+ * clear_page (unsigned long page)
+ *                    a2
+ */
 
 ENTRY(clear_page)
 	entry	a1, 16
-	addi	a4, a2, PAGE_SIZE
-	movi	a3, 0
 
-1:	s32i	a3, a2, 0
+	movi	a3, 0
+	__loopi	a2, a7, PAGE_SIZE, 32
+	s32i	a3, a2, 0
 	s32i	a3, a2, 4
 	s32i	a3, a2, 8
 	s32i	a3, a2, 12
@@ -37,42 +41,277 @@ ENTRY(clear_page)
 	s32i	a3, a2, 20
 	s32i	a3, a2, 24
 	s32i	a3, a2, 28
-	addi	a2, a2, 32
-	blt	a2, a4, 1b
+	__endla	a2, a7, 32
 
 	retw
 
 /*
+ * copy_page and copy_user_page are the same for non-cache-aliased configs.
+ *
  * copy_page (void *to, void *from)
- *                  a2        a3
+ *               a2          a3
  */
 
 ENTRY(copy_page)
 	entry	a1, 16
-	addi	a4, a2, PAGE_SIZE
-
-1:	l32i	a5, a3, 0
-	l32i	a6, a3, 4
-	l32i	a7, a3, 8
-	s32i	a5, a2, 0
-	s32i	a6, a2, 4
-	s32i	a7, a2, 8
-	l32i	a5, a3, 12
-	l32i	a6, a3, 16
-	l32i	a7, a3, 20
-	s32i	a5, a2, 12
-	s32i	a6, a2, 16
-	s32i	a7, a2, 20
-	l32i	a5, a3, 24
-	l32i	a6, a3, 28
-	s32i	a5, a2, 24
-	s32i	a6, a2, 28
-	addi	a2, a2, 32
-	addi	a3, a3, 32
-	blt	a2, a4, 1b
 
+	__loopi a2, a4, PAGE_SIZE, 32
+
+	l32i    a8, a3, 0
+	l32i    a9, a3, 4
+	s32i    a8, a2, 0
+	s32i    a9, a2, 4
+
+	l32i    a8, a3, 8
+	l32i    a9, a3, 12
+	s32i    a8, a2, 8
+	s32i    a9, a2, 12
+
+	l32i    a8, a3, 16
+	l32i    a9, a3, 20
+	s32i    a8, a2, 16
+	s32i    a9, a2, 20
+
+	l32i    a8, a3, 24
+	l32i    a9, a3, 28
+	s32i    a8, a2, 24
+	s32i    a9, a2, 28
+
+	addi    a2, a2, 32
+	addi    a3, a3, 32
+
+	__endl  a2, a4
+
+	retw
+
+/*
+ * If we have to deal with cache aliasing, we use temporary memory mappings
+ * to ensure that the source and destination pages have the same color as
+ * the virtual address. We use way 0 and 1 for temporary mappings in such cases.
+ *
+ * The temporary DTLB entries shouldn't be flushed by interrupts, but are
+ * flushed by preemptive task switches. Special code in the 
+ * fast_second_level_miss handler re-established the temporary mapping. 
+ * It requires that the PPNs for the destination and source addresses are
+ * in a6, and a7, respectively.
+ */
+
+/* TLB miss exceptions are treated special in the following region */
+
+ENTRY(__tlbtemp_mapping_start)
+
+#if (DCACHE_WAY_SIZE > PAGE_SIZE)
+
+/*
+ * clear_user_page (void *addr, unsigned long vaddr, struct page *page)
+ *                     a2              a3                 a4
+ */
+
+ENTRY(clear_user_page)
+	entry	a1, 32
+
+	/* Mark page dirty and determine alias. */
+
+	movi	a7, (1 << PG_ARCH_1)
+	l32i	a5, a4, PAGE_FLAGS
+	xor	a6, a2, a3
+	extui	a3, a3, PAGE_SHIFT, DCACHE_ALIAS_ORDER
+	extui	a6, a6, PAGE_SHIFT, DCACHE_ALIAS_ORDER
+	or	a5, a5, a7
+	slli	a3, a3, PAGE_SHIFT
+	s32i	a5, a4, PAGE_FLAGS
+
+	/* Skip setting up a temporary DTLB if not aliased. */
+
+	beqz	a6, 1f
+
+	/* Invalidate kernel page. */
+
+	mov	a10, a2
+	call8	__invalidate_dcache_page
+
+	/* Setup a temporary DTLB with the color of the VPN */
+
+	movi	a4, -PAGE_OFFSET + (PAGE_KERNEL | _PAGE_HW_WRITE)
+	movi	a5, TLBTEMP_BASE_1			# virt
+	add	a6, a2, a4				# ppn
+	add	a2, a5, a3				# add 'color'
+
+	wdtlb	a6, a2
+	dsync
+
+1:	movi	a3, 0
+	__loopi	a2, a7, PAGE_SIZE, 32
+	s32i	a3, a2, 0
+	s32i	a3, a2, 4
+	s32i	a3, a2, 8
+	s32i	a3, a2, 12
+	s32i	a3, a2, 16
+	s32i	a3, a2, 20
+	s32i	a3, a2, 24
+	s32i	a3, a2, 28
+	__endla	a2, a7, 32
+
+	bnez	a6, 1f
+	retw
+
+	/* We need to invalidate the temporary idtlb entry, if any. */
+
+1:	addi	a2, a2, -PAGE_SIZE
+	idtlb	a2
+	dsync
+
+	retw
+
+/*
+ * copy_page_user (void *to, void *from, unsigned long vaddr, struct page *page)
+ *                    a2          a3	        a4		    a5
+ */
+
+ENTRY(copy_user_page)
+
+	entry	a1, 32 
+
+	/* Mark page dirty and determine alias for destination. */
+
+	movi	a8, (1 << PG_ARCH_1)
+	l32i	a9, a5, PAGE_FLAGS
+	xor	a6, a2, a4
+	xor	a7, a3, a4
+	extui	a4, a4, PAGE_SHIFT, DCACHE_ALIAS_ORDER
+	extui	a6, a6, PAGE_SHIFT, DCACHE_ALIAS_ORDER
+	extui	a7, a7, PAGE_SHIFT, DCACHE_ALIAS_ORDER
+	or	a9, a9, a8
+	slli	a4, a4, PAGE_SHIFT
+	s32i	a9, a5, PAGE_FLAGS
+	movi	a5, -PAGE_OFFSET + (PAGE_KERNEL | _PAGE_HW_WRITE)
+
+	beqz	a6, 1f
+
+	/* Invalidate dcache */
+
+	mov	a10, a2
+	call8	__invalidate_dcache_page
+
+	/* Setup a temporary DTLB with a matching color. */
+
+	movi	a8, TLBTEMP_BASE_1			# base
+	add	a6, a2, a5				# ppn
+	add	a2, a8, a4				# add 'color'
+
+	wdtlb	a6, a2
+	dsync
+
+	/* Skip setting up a temporary DTLB for destination if not aliased. */
+
+1:	beqz	a7, 1f
+
+	/* Setup a temporary DTLB with a matching color. */
+
+	movi	a8, TLBTEMP_BASE_2			# base
+	add	a7, a3, a5				# ppn
+	add	a3, a8, a4
+	addi	a8, a3, 1				# way1
+
+	wdtlb	a7, a8
+	dsync
+
+1:	__loopi a2, a4, PAGE_SIZE, 32
+
+	l32i    a8, a3, 0
+	l32i    a9, a3, 4
+	s32i    a8, a2, 0
+	s32i    a9, a2, 4
+
+	l32i    a8, a3, 8
+	l32i    a9, a3, 12
+	s32i    a8, a2, 8
+	s32i    a9, a2, 12
+
+	l32i    a8, a3, 16
+	l32i    a9, a3, 20
+	s32i    a8, a2, 16
+	s32i    a9, a2, 20
+
+	l32i    a8, a3, 24
+	l32i    a9, a3, 28
+	s32i    a8, a2, 24
+	s32i    a9, a2, 28
+
+	addi    a2, a2, 32
+	addi    a3, a3, 32
+
+	__endl  a2, a4
+
+	/* We need to invalidate any temporary mapping! */
+
+	bnez	a6, 1f
+	bnez	a7, 2f
+	retw
+
+1:	addi	a2, a2, -PAGE_SIZE
+	idtlb	a2
+	dsync
+	bnez	a7, 2f
+	retw
+
+2:	addi	a3, a3, -PAGE_SIZE+1
+	idtlb	a3
+	dsync
+
+	retw
+
+#endif
+
+#if (DCACHE_WAY_SIZE > PAGE_SIZE)
+
+/*
+ * void __flush_invalidate_dcache_page_alias (addr, phys)
+ *                                             a2    a3
+ */
+
+ENTRY(__flush_invalidate_dcache_page_alias)
+	entry	sp, 16
+
+	movi	a7, 0			# required for exception handler
+	addi	a6, a3, (PAGE_KERNEL | _PAGE_HW_WRITE)
+	mov	a4, a2
+	wdtlb	a6, a2
+	dsync
+
+	___flush_invalidate_dcache_page a2 a3
+
+	idtlb	a4
+	dsync
+
+	retw
+
+#endif
+
+ENTRY(__tlbtemp_mapping_itlb)
+
+#if (ICACHE_WAY_SIZE > PAGE_SIZE)
+	
+ENTRY(__invalidate_icache_page_alias)
+	entry	sp, 16
+
+	addi	a6, a3, (PAGE_KERNEL | _PAGE_HW_WRITE)
+	mov	a4, a2
+	witlb	a6, a2
+	isync
+
+	___invalidate_icache_page a2 a3
+
+	iitlb	a4
+	isync
 	retw
 
+#endif
+
+/* End of special treatment in tlb miss exception */
+
+ENTRY(__tlbtemp_mapping_end)
+
 /*
  * void __invalidate_icache_page(ulong start)
  */
@@ -121,8 +360,6 @@ ENTRY(__flush_dcache_page)
 	dsync
 	retw
 
-
-
 /*
  * void __invalidate_icache_range(ulong start, ulong size)
  */
@@ -168,7 +405,6 @@ ENTRY(__invalidate_dcache_range)
 
 	___invalidate_dcache_range a2 a3 a4
 
-
 	retw
 
 /*