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Subject[PATCH 21/46] x86, mm: setup page table in top-down
Date
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.

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.

Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
arch/x86/include/asm/page_types.h | 1 +
arch/x86/include/asm/pgtable.h | 1 +
arch/x86/kernel/setup.c | 3 +
arch/x86/mm/init.c | 210 +++++++++++--------------------------
arch/x86/mm/init_32.c | 17 +++-
arch/x86/mm/init_64.c | 17 +++-
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 54c9787..9f6f3e6 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 dd1a888..6991a3e 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 94f922a..f7634092 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 47a1ba2..76a6e82 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;

@@ -392,17 +308,14 @@ 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.
+ * this one could take range with hole in it.
*/
-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) {
@@ -422,71 +335,70 @@ 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 27f7fc6..7bb1106 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 fa28e3e..eefaea6 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);
--
1.7.7


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