x86, mm: setup page table in top-down

Get pgt_buf early from BRK, and use it to map PMD_SIZE from top at first.
Then use mapped pages to map more ranges below, and keep looping until
all pages get mapped.

alloc_low_page will use page from BRK at first, after that buffer is used
up, will use memblock to find and reserve pages for page table usage.

Introduce min_pfn_mapped to make sure find new pages from mapped ranges,
that will be updated when lower pages get mapped.

Also add step_size to make sure that don't try to map too big range with
limited mapped pages initially, and increase the step_size when we have
more mapped pages on hand.

We don't need to call pagetable_reserve anymore, reserve work is done
in alloc_low_page() directly.

At last we can get rid of calculation and find early pgt related code.

-v2: update to after fix_xen change,
     also use MACRO for initial pgt_buf size and add comments with it.
-v3: skip big reserved range in memblock.reserved near end.
-v4: don't need fix_xen change now.
-v5: add changelog about moving about reserving pagetable to alloc_low_page.

Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-22-git-send-email-yinghai@kernel.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

6 files changed, 94 insertions, 155 deletions

diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
index 54c97879195e..9f6f3e66e84d 100644
--- a/arch/x86/include/asm/page_types.h
+++ b/arch/x86/include/asm/page_types.h
@@ -45,6 +45,7 @@ extern int devmem_is_allowed(unsigned long pagenr);
 
 extern unsigned long max_low_pfn_mapped;
 extern unsigned long max_pfn_mapped;
+extern unsigned long min_pfn_mapped;
 
 static inline phys_addr_t get_max_mapped(void)
 {
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index dd1a88832d25..6991a3e1bf81 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -603,6 +603,7 @@ static inline int pgd_none(pgd_t pgd)
 
 extern int direct_gbpages;
 void init_mem_mapping(void);
+void early_alloc_pgt_buf(void);
 
 /* local pte updates need not use xchg for locking */
 static inline pte_t native_local_ptep_get_and_clear(pte_t *ptep)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 94f922a73c54..f7634092931b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -124,6 +124,7 @@
  */
 unsigned long max_low_pfn_mapped;
 unsigned long max_pfn_mapped;
+unsigned long min_pfn_mapped;
 
 #ifdef CONFIG_DMI
 RESERVE_BRK(dmi_alloc, 65536);
@@ -900,6 +901,8 @@ void __init setup_arch(char **cmdline_p)
 
         reserve_ibft_region();
 
+        early_alloc_pgt_buf();
+
         /*
          * Need to conclude brk, before memblock_x86_fill()
          *  it could use memblock_find_in_range, could overlap with
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index c688ea3887f2..2393d0099e7f 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -21,6 +21,21 @@ unsigned long __initdata pgt_buf_start;
 unsigned long __meminitdata pgt_buf_end;
 unsigned long __meminitdata pgt_buf_top;
 
+/* need 4 4k for initial PMD_SIZE, 4k for 0-ISA_END_ADDRESS */
+#define INIT_PGT_BUF_SIZE       (5 * PAGE_SIZE)
+RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE);
+void  __init early_alloc_pgt_buf(void)
+{
+        unsigned long tables = INIT_PGT_BUF_SIZE;
+        phys_addr_t base;
+
+        base = __pa(extend_brk(tables, PAGE_SIZE));
+
+        pgt_buf_start = base >> PAGE_SHIFT;
+        pgt_buf_end = pgt_buf_start;
+        pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT);
+}
+
 int after_bootmem;
 
 int direct_gbpages
@@ -228,105 +243,6 @@ static int __meminit split_mem_range(struct map_range *mr, int nr_range,
         return nr_range;
 }
 
-/*
- * First calculate space needed for kernel direct mapping page tables to cover
- * mr[0].start to mr[nr_range - 1].end, while accounting for possible 2M and 1GB
- * pages. Then find enough contiguous space for those page tables.
- */
-static unsigned long __init calculate_table_space_size(unsigned long start, unsigned long end)
-{
-        int i;
-        unsigned long puds = 0, pmds = 0, ptes = 0, tables;
-        struct map_range mr[NR_RANGE_MR];
-        int nr_range;
-
-        memset(mr, 0, sizeof(mr));
-        nr_range = 0;
-        nr_range = split_mem_range(mr, nr_range, start, end);
-
-        for (i = 0; i < nr_range; i++) {
-                unsigned long range, extra;
-
-                range = mr[i].end - mr[i].start;
-                puds += (range + PUD_SIZE - 1) >> PUD_SHIFT;
-
-                if (mr[i].page_size_mask & (1 << PG_LEVEL_1G)) {
-                        extra = range - ((range >> PUD_SHIFT) << PUD_SHIFT);
-                        pmds += (extra + PMD_SIZE - 1) >> PMD_SHIFT;
-                } else {
-                        pmds += (range + PMD_SIZE - 1) >> PMD_SHIFT;
-                }
-
-                if (mr[i].page_size_mask & (1 << PG_LEVEL_2M)) {
-                        extra = range - ((range >> PMD_SHIFT) << PMD_SHIFT);
-#ifdef CONFIG_X86_32
-                        extra += PMD_SIZE;
-#endif
-                        ptes += (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
-                } else {
-                        ptes += (range + PAGE_SIZE - 1) >> PAGE_SHIFT;
-                }
-        }
-
-        tables = roundup(puds * sizeof(pud_t), PAGE_SIZE);
-        tables += roundup(pmds * sizeof(pmd_t), PAGE_SIZE);
-        tables += roundup(ptes * sizeof(pte_t), PAGE_SIZE);
-
-#ifdef CONFIG_X86_32
-        /* for fixmap */
-        tables += roundup(__end_of_fixed_addresses * sizeof(pte_t), PAGE_SIZE);
-#endif
-
-        return tables;
-}
-
-static unsigned long __init calculate_all_table_space_size(void)
-{
-        unsigned long start_pfn, end_pfn;
-        unsigned long tables;
-        int i;
-
-        /* the ISA range is always mapped regardless of memory holes */
-        tables = calculate_table_space_size(0, ISA_END_ADDRESS);
-
-        for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
-                u64 start = start_pfn << PAGE_SHIFT;
-                u64 end = end_pfn << PAGE_SHIFT;
-
-                if (end <= ISA_END_ADDRESS)
-                        continue;
-
-                if (start < ISA_END_ADDRESS)
-                        start = ISA_END_ADDRESS;
-#ifdef CONFIG_X86_32
-                /* on 32 bit, we only map up to max_low_pfn */
-                if ((start >> PAGE_SHIFT) >= max_low_pfn)
-                        continue;
-
-                if ((end >> PAGE_SHIFT) > max_low_pfn)
-                        end = max_low_pfn << PAGE_SHIFT;
-#endif
-                tables += calculate_table_space_size(start, end);
-        }
-
-        return tables;
-}
-
-static void __init find_early_table_space(unsigned long start,
-                                          unsigned long good_end,
-                                          unsigned long tables)
-{
-        phys_addr_t base;
-
-        base = memblock_find_in_range(start, good_end, tables, PAGE_SIZE);
-        if (!base)
-                panic("Cannot find space for the kernel page tables");
-
-        pgt_buf_start = base >> PAGE_SHIFT;
-        pgt_buf_end = pgt_buf_start;
-        pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT);
-}
-
 static struct range pfn_mapped[E820_X_MAX];
 static int nr_pfn_mapped;
 
@@ -391,17 +307,14 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
 }
 
 /*
- * Iterate through E820 memory map and create direct mappings for only E820_RAM
- * regions. We cannot simply create direct mappings for all pfns from
- * [0 to max_low_pfn) and [4GB to max_pfn) because of possible memory holes in
- * high addresses that cannot be marked as UC by fixed/variable range MTRRs.
- * Depending on the alignment of E820 ranges, this may possibly result in using
- * smaller size (i.e. 4K instead of 2M or 1G) page tables.
+ * would have hole in the middle or ends, and only ram parts will be mapped.
  */
-static void __init init_range_memory_mapping(unsigned long range_start,
+static unsigned long __init init_range_memory_mapping(
+                                           unsigned long range_start,
                                            unsigned long range_end)
 {
         unsigned long start_pfn, end_pfn;
+        unsigned long mapped_ram_size = 0;
         int i;
 
         for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
@@ -421,71 +334,70 @@ static void __init init_range_memory_mapping(unsigned long range_start,
                         end = range_end;
 
                 init_memory_mapping(start, end);
+
+                mapped_ram_size += end - start;
         }
+
+        return mapped_ram_size;
 }
 
+/* (PUD_SHIFT-PMD_SHIFT)/2 */
+#define STEP_SIZE_SHIFT 5
 void __init init_mem_mapping(void)
 {
-        unsigned long tables, good_end, end;
+        unsigned long end, real_end, start, last_start;
+        unsigned long step_size;
+        unsigned long addr;
+        unsigned long mapped_ram_size = 0;
+        unsigned long new_mapped_ram_size;
 
         probe_page_size_mask();
 
-        /*
-         * Find space for the kernel direct mapping tables.
-         *
-         * Later we should allocate these tables in the local node of the
-         * memory mapped. Unfortunately this is done currently before the
-         * nodes are discovered.
-         */
 #ifdef CONFIG_X86_64
         end = max_pfn << PAGE_SHIFT;
-        good_end = end;
 #else
         end = max_low_pfn << PAGE_SHIFT;
-        good_end = max_pfn_mapped << PAGE_SHIFT;
 #endif
-        tables = calculate_all_table_space_size();
-        find_early_table_space(0, good_end, tables);
-        printk(KERN_DEBUG "kernel direct mapping tables up to %#lx @ [mem %#010lx-%#010lx] prealloc\n",
-                end - 1, pgt_buf_start << PAGE_SHIFT,
-                (pgt_buf_top << PAGE_SHIFT) - 1);
 
-        max_pfn_mapped = 0; /* will get exact value next */
         /* the ISA range is always mapped regardless of memory holes */
         init_memory_mapping(0, ISA_END_ADDRESS);
-        init_range_memory_mapping(ISA_END_ADDRESS, end);
+
+        /* xen has big range in reserved near end of ram, skip it at first */
+        addr = memblock_find_in_range(ISA_END_ADDRESS, end, PMD_SIZE,
+                         PAGE_SIZE);
+        real_end = addr + PMD_SIZE;
+
+        /* step_size need to be small so pgt_buf from BRK could cover it */
+        step_size = PMD_SIZE;
+        max_pfn_mapped = 0; /* will get exact value next */
+        min_pfn_mapped = real_end >> PAGE_SHIFT;
+        last_start = start = real_end;
+        while (last_start > ISA_END_ADDRESS) {
+                if (last_start > step_size) {
+                        start = round_down(last_start - 1, step_size);
+                        if (start < ISA_END_ADDRESS)
+                                start = ISA_END_ADDRESS;
+                } else
+                        start = ISA_END_ADDRESS;
+                new_mapped_ram_size = init_range_memory_mapping(start,
+                                                        last_start);
+                last_start = start;
+                min_pfn_mapped = last_start >> PAGE_SHIFT;
+                /* only increase step_size after big range get mapped */
+                if (new_mapped_ram_size > mapped_ram_size)
+                        step_size <<= STEP_SIZE_SHIFT;
+                mapped_ram_size += new_mapped_ram_size;
+        }
+
+        if (real_end < end)
+                init_range_memory_mapping(real_end, end);
+
 #ifdef CONFIG_X86_64
         if (max_pfn > max_low_pfn) {
                 /* can we preseve max_low_pfn ?*/
                 max_low_pfn = max_pfn;
         }
 #endif
-        /*
-         * Reserve the kernel pagetable pages we used (pgt_buf_start -
-         * pgt_buf_end) and free the other ones (pgt_buf_end - pgt_buf_top)
-         * so that they can be reused for other purposes.
-         *
-         * On native it just means calling memblock_reserve, on Xen it also
-         * means marking RW the pagetable pages that we allocated before
-         * but that haven't been used.
-         *
-         * In fact on xen we mark RO the whole range pgt_buf_start -
-         * pgt_buf_top, because we have to make sure that when
-         * init_memory_mapping reaches the pagetable pages area, it maps
-         * RO all the pagetable pages, including the ones that are beyond
-         * pgt_buf_end at that time.
-         */
-        if (pgt_buf_end > pgt_buf_start) {
-                printk(KERN_DEBUG "kernel direct mapping tables up to %#lx @ [mem %#010lx-%#010lx] final\n",
-                        end - 1, pgt_buf_start << PAGE_SHIFT,
-                        (pgt_buf_end << PAGE_SHIFT) - 1);
-                x86_init.mapping.pagetable_reserve(PFN_PHYS(pgt_buf_start),
-                                PFN_PHYS(pgt_buf_end));
-        }
-
-        /* stop the wrong using */
-        pgt_buf_top = 0;
-
         early_memtest(0, max_pfn_mapped << PAGE_SHIFT);
 }
 
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 27f7fc69cf8a..7bb11064a9e1 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -61,11 +61,22 @@ bool __read_mostly __vmalloc_start_set = false;
 
 static __init void *alloc_low_page(void)
 {
-        unsigned long pfn = pgt_buf_end++;
+        unsigned long pfn;
         void *adr;
 
-        if (pfn >= pgt_buf_top)
-                panic("alloc_low_page: ran out of memory");
+        if ((pgt_buf_end + 1) >= pgt_buf_top) {
+                unsigned long ret;
+                if (min_pfn_mapped >= max_pfn_mapped)
+                        panic("alloc_low_page: ran out of memory");
+                ret = memblock_find_in_range(min_pfn_mapped << PAGE_SHIFT,
+                                        max_pfn_mapped << PAGE_SHIFT,
+                                        PAGE_SIZE, PAGE_SIZE);
+                if (!ret)
+                        panic("alloc_low_page: can not alloc memory");
+                memblock_reserve(ret, PAGE_SIZE);
+                pfn = ret >> PAGE_SHIFT;
+        } else
+                pfn = pgt_buf_end++;
 
         adr = __va(pfn * PAGE_SIZE);
         clear_page(adr);
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index fa28e3e29741..eefaea637b3d 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -316,7 +316,7 @@ void __init cleanup_highmap(void)
 
 static __ref void *alloc_low_page(unsigned long *phys)
 {
-        unsigned long pfn = pgt_buf_end++;
+        unsigned long pfn;
         void *adr;
 
         if (after_bootmem) {
@@ -326,8 +326,19 @@ static __ref void *alloc_low_page(unsigned long *phys)
                 return adr;
         }
 
-        if (pfn >= pgt_buf_top)
-                panic("alloc_low_page: ran out of memory");
+        if ((pgt_buf_end + 1) >= pgt_buf_top) {
+                unsigned long ret;
+                if (min_pfn_mapped >= max_pfn_mapped)
+                        panic("alloc_low_page: ran out of memory");
+                ret = memblock_find_in_range(min_pfn_mapped << PAGE_SHIFT,
+                                        max_pfn_mapped << PAGE_SHIFT,
+                                        PAGE_SIZE, PAGE_SIZE);
+                if (!ret)
+                        panic("alloc_low_page: can not alloc memory");
+                memblock_reserve(ret, PAGE_SIZE);
+                pfn = ret >> PAGE_SHIFT;
+        } else
+                pfn = pgt_buf_end++;
 
         adr = early_memremap(pfn * PAGE_SIZE, PAGE_SIZE);
         clear_page(adr);