xtensa: add HIGHMEM support

Introduce fixmap area just below the vmalloc region. Use it for atomic
mapping of high memory pages.
High memory on cores with cache aliasing is not supported and is still
to be implemented. Fail build for such configurations for now.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

5 files changed, 146 insertions, 15 deletions

diff --git a/arch/xtensa/mm/Makefile b/arch/xtensa/mm/Makefile
index f0b646d..f54f78e 100644
--- a/arch/xtensa/mm/Makefile
+++ b/arch/xtensa/mm/Makefile
@@ -4,3 +4,4 @@
 
 obj-y			:= init.o cache.o misc.o
 obj-$(CONFIG_MMU)	+= fault.o mmu.o tlb.o
+obj-$(CONFIG_HIGHMEM)	+= highmem.o
diff --git a/arch/xtensa/mm/cache.c b/arch/xtensa/mm/cache.c
index ba4c47f..63cbb86 100644
--- a/arch/xtensa/mm/cache.c
+++ b/arch/xtensa/mm/cache.c
@@ -59,6 +59,10 @@
  *
  */
 
+#if (DCACHE_WAY_SIZE > PAGE_SIZE) && defined(CONFIG_HIGHMEM)
+#error "HIGHMEM is not supported on cores with aliasing cache."
+#endif
+
 #if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
 
 /*
@@ -179,10 +183,11 @@ update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t *ptep)
 #else
 	if (!PageReserved(page) && !test_bit(PG_arch_1, &page->flags)
 	    && (vma->vm_flags & VM_EXEC) != 0) {
-	    	unsigned long paddr = (unsigned long) page_address(page);
+		unsigned long paddr = (unsigned long)kmap_atomic(page);
 		__flush_dcache_page(paddr);
 		__invalidate_icache_page(paddr);
 		set_bit(PG_arch_1, &page->flags);
+		kunmap_atomic((void *)paddr);
 	}
 #endif
 }
diff --git a/arch/xtensa/mm/highmem.c b/arch/xtensa/mm/highmem.c
new file mode 100644
index 0000000..17a8c0d
--- /dev/null
+++ b/arch/xtensa/mm/highmem.c
@@ -0,0 +1,72 @@
+/*
+ * High memory support for Xtensa architecture
+ *
+ * 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) 2014 Cadence Design Systems Inc.
+ */
+
+#include <linux/export.h>
+#include <linux/highmem.h>
+#include <asm/tlbflush.h>
+
+static pte_t *kmap_pte;
+
+void *kmap_atomic(struct page *page)
+{
+	enum fixed_addresses idx;
+	unsigned long vaddr;
+	int type;
+
+	pagefault_disable();
+	if (!PageHighMem(page))
+		return page_address(page);
+
+	type = kmap_atomic_idx_push();
+	idx = type + KM_TYPE_NR * smp_processor_id();
+	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+#ifdef CONFIG_DEBUG_HIGHMEM
+	BUG_ON(!pte_none(*(kmap_pte - idx)));
+#endif
+	set_pte(kmap_pte - idx, mk_pte(page, PAGE_KERNEL_EXEC));
+
+	return (void *)vaddr;
+}
+EXPORT_SYMBOL(kmap_atomic);
+
+void __kunmap_atomic(void *kvaddr)
+{
+	int idx, type;
+
+	if (kvaddr >= (void *)FIXADDR_START &&
+	    kvaddr < (void *)FIXADDR_TOP) {
+		type = kmap_atomic_idx();
+		idx = type + KM_TYPE_NR * smp_processor_id();
+
+		/*
+		 * Force other mappings to Oops if they'll try to access this
+		 * pte without first remap it.  Keeping stale mappings around
+		 * is a bad idea also, in case the page changes cacheability
+		 * attributes or becomes a protected page in a hypervisor.
+		 */
+		pte_clear(&init_mm, kvaddr, kmap_pte - idx);
+		local_flush_tlb_kernel_range((unsigned long)kvaddr,
+					     (unsigned long)kvaddr + PAGE_SIZE);
+
+		kmap_atomic_idx_pop();
+	}
+
+	pagefault_enable();
+}
+EXPORT_SYMBOL(__kunmap_atomic);
+
+void __init kmap_init(void)
+{
+	unsigned long kmap_vstart;
+
+	/* cache the first kmap pte */
+	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
+	kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
+}
diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
index 03bd025..4224256 100644
--- a/arch/xtensa/mm/init.c
+++ b/arch/xtensa/mm/init.c
@@ -20,6 +20,7 @@
 #include <linux/errno.h>
 #include <linux/bootmem.h>
 #include <linux/gfp.h>
+#include <linux/highmem.h>
 #include <linux/swap.h>
 #include <linux/mman.h>
 #include <linux/nodemask.h>
@@ -296,19 +297,13 @@ void __init bootmem_init(void)
 
 void __init zones_init(void)
 {
-	unsigned long zones_size[MAX_NR_ZONES];
-	int i;
-
 	/* All pages are DMA-able, so we put them all in the DMA zone. */
-
-	zones_size[ZONE_DMA] = max_low_pfn - ARCH_PFN_OFFSET;
-	for (i = 1; i < MAX_NR_ZONES; i++)
-		zones_size[i] = 0;
-
+	unsigned long zones_size[MAX_NR_ZONES] = {
+		[ZONE_DMA] = max_low_pfn - ARCH_PFN_OFFSET,
 #ifdef CONFIG_HIGHMEM
-	zones_size[ZONE_HIGHMEM] = max_pfn - max_low_pfn;
+		[ZONE_HIGHMEM] = max_pfn - max_low_pfn,
 #endif
-
+	};
 	free_area_init_node(0, zones_size, ARCH_PFN_OFFSET, NULL);
 }
 
@@ -318,16 +313,38 @@ void __init zones_init(void)
 
 void __init mem_init(void)
 {
-	max_mapnr = max_low_pfn - ARCH_PFN_OFFSET;
-	high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
-
 #ifdef CONFIG_HIGHMEM
-#error HIGHGMEM not implemented in init.c
+	unsigned long tmp;
+
+	reset_all_zones_managed_pages();
+	for (tmp = max_low_pfn; tmp < max_pfn; tmp++)
+		free_highmem_page(pfn_to_page(tmp));
 #endif
 
+	max_mapnr = max_pfn - ARCH_PFN_OFFSET;
+	high_memory = (void *)__va(max_low_pfn << PAGE_SHIFT);
+
 	free_all_bootmem();
 
 	mem_init_print_info(NULL);
+	pr_info("virtual kernel memory layout:\n"
+#ifdef CONFIG_HIGHMEM
+		"    pkmap   : 0x%08lx - 0x%08lx  (%5lu kB)\n"
+		"    fixmap  : 0x%08lx - 0x%08lx  (%5lu kB)\n"
+#endif
+		"    vmalloc : 0x%08x - 0x%08x  (%5u MB)\n"
+		"    lowmem  : 0x%08x - 0x%08lx  (%5lu MB)\n",
+#ifdef CONFIG_HIGHMEM
+		PKMAP_BASE, PKMAP_BASE + LAST_PKMAP * PAGE_SIZE,
+		(LAST_PKMAP*PAGE_SIZE) >> 10,
+		FIXADDR_START, FIXADDR_TOP,
+		(FIXADDR_TOP - FIXADDR_START) >> 10,
+#endif
+		VMALLOC_START, VMALLOC_END,
+		(VMALLOC_END - VMALLOC_START) >> 20,
+		PAGE_OFFSET, PAGE_OFFSET +
+		(max_low_pfn - min_low_pfn) * PAGE_SIZE,
+		((max_low_pfn - min_low_pfn) * PAGE_SIZE) >> 20);
 }
 
 #ifdef CONFIG_BLK_DEV_INITRD
diff --git a/arch/xtensa/mm/mmu.c b/arch/xtensa/mm/mmu.c
index 861203e..3429b48 100644
--- a/arch/xtensa/mm/mmu.c
+++ b/arch/xtensa/mm/mmu.c
@@ -3,6 +3,7 @@
  *
  * Extracted from init.c
  */
+#include <linux/bootmem.h>
 #include <linux/percpu.h>
 #include <linux/init.h>
 #include <linux/string.h>
@@ -16,9 +17,44 @@
 #include <asm/initialize_mmu.h>
 #include <asm/io.h>
 
+#if defined(CONFIG_HIGHMEM)
+static void * __init init_pmd(unsigned long vaddr)
+{
+	pgd_t *pgd = pgd_offset_k(vaddr);
+	pmd_t *pmd = pmd_offset(pgd, vaddr);
+
+	if (pmd_none(*pmd)) {
+		unsigned i;
+		pte_t *pte = alloc_bootmem_low_pages(PAGE_SIZE);
+
+		for (i = 0; i < 1024; i++)
+			pte_clear(NULL, 0, pte + i);
+
+		set_pmd(pmd, __pmd(((unsigned long)pte) & PAGE_MASK));
+		BUG_ON(pte != pte_offset_kernel(pmd, 0));
+		pr_debug("%s: vaddr: 0x%08lx, pmd: 0x%p, pte: 0x%p\n",
+			 __func__, vaddr, pmd, pte);
+		return pte;
+	} else {
+		return pte_offset_kernel(pmd, 0);
+	}
+}
+
+static void __init fixedrange_init(void)
+{
+	BUILD_BUG_ON(FIXADDR_SIZE > PMD_SIZE);
+	init_pmd(__fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK);
+}
+#endif
+
 void __init paging_init(void)
 {
 	memset(swapper_pg_dir, 0, PAGE_SIZE);
+#ifdef CONFIG_HIGHMEM
+	fixedrange_init();
+	pkmap_page_table = init_pmd(PKMAP_BASE);
+	kmap_init();
+#endif
 }
 
 /*