Re: [PATCH] x86: fix init_memory_mapping over boundary v4

From: Jeremy Fitzhardinge
Date: Sat Jun 28 2008 - 22:22:52 EST

Yinghai Lu wrote:
some end boundary is only page alignment, instead of 2M alignment,
so call ker_phycial_mapping_init three times.
then don't overmap above the max_low_pfn

v2: make init_memory_mapping more solid: start could be any value other than 0
v3: fix NON PAE by handling left over in kernel_physical_mapping
v4: revert back to v2, and use PMD_SHIFT to calculate boundary
also adjust size for pre-allocated table size

Signed-off-by: Yinghai Lu <yhlu.kernel@xxxxxxxxx>

---
arch/x86/mm/init_32.c | 101 +++++++++++++++++++++++++++++++++++++-------------
1 file changed, 75 insertions(+), 26 deletions(-)

Index: linux-2.6/arch/x86/mm/init_32.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_32.c
+++ linux-2.6/arch/x86/mm/init_32.c
@@ -184,8 +184,9 @@ static inline int is_kernel_text(unsigne
* PAGE_OFFSET:
*/
static void __init kernel_physical_mapping_init(pgd_t *pgd_base,
- unsigned long start,
- unsigned long end)
+ unsigned long start_pfn,
+ unsigned long end_pfn,
+ int use_pse)
{
int pgd_idx, pmd_idx, pte_ofs;
unsigned long pfn;
@@ -193,32 +194,33 @@ static void __init kernel_physical_mappi
pmd_t *pmd;
pte_t *pte;
unsigned pages_2m = 0, pages_4k = 0;
- unsigned limit_pfn = end >> PAGE_SHIFT;
- pgd_idx = pgd_index(PAGE_OFFSET);
- pgd = pgd_base + pgd_idx;
- pfn = start >> PAGE_SHIFT;
+ if (!cpu_has_pse)
+ use_pse = 0;
+ pfn = start_pfn;
+ pgd_idx = pgd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
+ pgd = pgd_base + pgd_idx;
for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
pmd = one_md_table_init(pgd);
- if (pfn >= limit_pfn)
- continue;
- for (pmd_idx = 0;
- pmd_idx < PTRS_PER_PMD && pfn < limit_pfn;
+ if (pfn >= end_pfn)
+ continue;
+#ifdef CONFIG_X86_PAE
+ pmd_idx = pmd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
+ pmd += pmd_idx;
+#else
+ pmd_idx = 0;
+#endif

We should really define X_index() to return 0 for folded pagetable level X. I've had to put similar #ifdefs in other code. Also, for the purposes of making this code more unifiable, it's probably better to test for "#if PAGETABLE_LEVELS >= 3" rather than for PAE specifically.

+ for (; pmd_idx < PTRS_PER_PMD && pfn < end_pfn;
pmd++, pmd_idx++) {
unsigned int addr = pfn * PAGE_SIZE + PAGE_OFFSET;
/*
* Map with big pages if possible, otherwise
* create normal page tables:
- *
- * Don't use a large page for the first 2/4MB of memory
- * because there are often fixed size MTRRs in there
- * and overlapping MTRRs into large pages can cause
- * slowdowns.
*/
- if (cpu_has_pse && !(pgd_idx == 0 && pmd_idx == 0)) {
+ if (use_pse) {
unsigned int addr2;
pgprot_t prot = PAGE_KERNEL_LARGE;
@@ -233,13 +235,13 @@ static void __init kernel_physical_mappi
set_pmd(pmd, pfn_pmd(pfn, prot));
pfn += PTRS_PER_PTE;
- max_pfn_mapped = pfn;
continue;
}
pte = one_page_table_init(pmd);
- for (pte_ofs = 0;
- pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn;
+ pte_ofs = pte_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
+ pte += pte_ofs;
+ for (; pte_ofs < PTRS_PER_PTE && pfn < end_pfn;
pte++, pfn++, pte_ofs++, addr += PAGE_SIZE) {
pgprot_t prot = PAGE_KERNEL;
@@ -249,7 +251,6 @@ static void __init kernel_physical_mappi
pages_4k++;
set_pte(pte, pfn_pte(pfn, prot));
}
- max_pfn_mapped = pfn;
}
}
update_page_count(PG_LEVEL_2M, pages_2m);
@@ -729,7 +730,7 @@ void __init setup_bootmem_allocator(void
static void __init find_early_table_space(unsigned long end)
{
- unsigned long puds, pmds, tables, start;
+ unsigned long puds, pmds, ptes, tables, start;
puds = (end + PUD_SIZE - 1) >> PUD_SHIFT;
tables = PAGE_ALIGN(puds * sizeof(pud_t));
@@ -737,10 +738,19 @@ static void __init find_early_table_spac
pmds = (end + PMD_SIZE - 1) >> PMD_SHIFT;
tables += PAGE_ALIGN(pmds * sizeof(pmd_t));
- if (!cpu_has_pse) {
- int ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
- tables += PAGE_ALIGN(ptes * sizeof(pte_t));
- }
+ if (cpu_has_pse) {
+ unsigned long extra;
+
+ extra = end - ((end>>PMD_SHIFT) << PMD_SHIFT);
+ extra += PMD_SIZE;

Is this the same as "extra = (end + PMD_SIZE + 1) & PMD_MASK"?

+ ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ } else
+ ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+ tables += PAGE_ALIGN(ptes * sizeof(pte_t));
+
+ /* for fixmap */
+ tables += PAGE_SIZE * 2;

Why not correct for fixmaps by putting "ptes += __end_of_fixed_addresses;" above?

/*
* RED-PEN putting page tables only on node 0 could
@@ -766,6 +776,8 @@ unsigned long __init_refok init_memory_m
unsigned long end)
{
pgd_t *pgd_base = swapper_pg_dir;
+ unsigned long start_pfn, end_pfn;
+ unsigned long big_page_start;
/*
* Find space for the kernel direct mapping tables.
@@ -790,7 +802,44 @@ unsigned long __init_refok init_memory_m
__PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
}
- kernel_physical_mapping_init(pgd_base, start, end);
+ /*
+ * Don't use a large page for the first 2/4MB of memory
+ * because there are often fixed size MTRRs in there
+ * and overlapping MTRRs into large pages can cause
+ * slowdowns.
+ */
+ big_page_start = PMD_SIZE;
+
+ if (start < big_page_start) {
+ start_pfn = start >> PAGE_SHIFT;
+ end_pfn = min(big_page_start>>PAGE_SHIFT, end>>PAGE_SHIFT);
+ } else {
+ /* head is not big page alignment ? */
+ start_pfn = start >> PAGE_SHIFT;
+ end_pfn = ((start + PMD_SIZE - 1)>>PMD_SHIFT)
+ << (PMD_SHIFT - PAGE_SHIFT);
+ }
+ if (start_pfn < end_pfn)
+ kernel_physical_mapping_init(pgd_base, start_pfn, end_pfn, 0);
+
+ /* big page range */
+ start_pfn = ((start + PMD_SIZE - 1)>>PMD_SHIFT)
+ << (PMD_SHIFT - PAGE_SHIFT);
+ if (start_pfn < (big_page_start >> PAGE_SHIFT))
+ start_pfn = big_page_start >> PAGE_SHIFT;
+ end_pfn = (end>>PMD_SHIFT) << (PMD_SHIFT - PAGE_SHIFT);
+ if (start_pfn < end_pfn)
+ kernel_physical_mapping_init(pgd_base, start_pfn, end_pfn,
+ cpu_has_pse);
+
+ /* tail is not big page alignment ? */
+ start_pfn = end_pfn;
+ if (start_pfn > (big_page_start>>PAGE_SHIFT)) {
+ end_pfn = end >> PAGE_SHIFT;
+ if (start_pfn < end_pfn)
+ kernel_physical_mapping_init(pgd_base, start_pfn,
+ end_pfn, 0);
+ }
early_ioremap_page_table_range_init(pgd_base);

J
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