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authorJacob Shin <jacob.shin@amd.com>2012-11-16 19:38:52 -0800
committerH. Peter Anvin <hpa@linux.intel.com>2012-11-17 11:59:14 -0800
commit66520ebc2df3fe52eb4792f8101fac573b766baf (patch)
treecc31359fa406833d946eff89ee8804b18e81c673 /arch/x86/mm/init.c
parente8c57d40519d7226acb8e662f3ab496202ebc7a6 (diff)
downloadlinux-66520ebc2df3fe52eb4792f8101fac573b766baf.tar.bz2
x86, mm: Only direct map addresses that are marked as E820_RAM
Currently direct mappings are created for [ 0 to max_low_pfn<<PAGE_SHIFT ) and [ 4GB to max_pfn<<PAGE_SHIFT ), which may include regions that are not backed by actual DRAM. This is fine for holes under 4GB which are covered by fixed and variable range MTRRs to be UC. However, we run into trouble on higher memory addresses which cannot be covered by MTRRs. Our system with 1TB of RAM has an e820 that looks like this: BIOS-e820: [mem 0x0000000000000000-0x00000000000983ff] usable BIOS-e820: [mem 0x0000000000098400-0x000000000009ffff] reserved BIOS-e820: [mem 0x00000000000d0000-0x00000000000fffff] reserved BIOS-e820: [mem 0x0000000000100000-0x00000000c7ebffff] usable BIOS-e820: [mem 0x00000000c7ec0000-0x00000000c7ed7fff] ACPI data BIOS-e820: [mem 0x00000000c7ed8000-0x00000000c7ed9fff] ACPI NVS BIOS-e820: [mem 0x00000000c7eda000-0x00000000c7ffffff] reserved BIOS-e820: [mem 0x00000000fec00000-0x00000000fec0ffff] reserved BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved BIOS-e820: [mem 0x00000000fff00000-0x00000000ffffffff] reserved BIOS-e820: [mem 0x0000000100000000-0x000000e037ffffff] usable BIOS-e820: [mem 0x000000e038000000-0x000000fcffffffff] reserved BIOS-e820: [mem 0x0000010000000000-0x0000011ffeffffff] usable and so direct mappings are created for huge memory hole between 0x000000e038000000 to 0x0000010000000000. Even though the kernel never generates memory accesses in that region, since the page tables mark them incorrectly as being WB, our (AMD) processor ends up causing a MCE while doing some memory bookkeeping/optimizations around that area. This patch iterates through e820 and only direct maps ranges that are marked as E820_RAM, and keeps track of those pfn ranges. 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. -v2: move changes from setup.c to mm/init.c, also use for_each_mem_pfn_range instead. - Yinghai Lu -v3: add calculate_all_table_space_size() to get correct needed page table size. - Yinghai Lu -v4: fix add_pfn_range_mapped() to get correct max_low_pfn_mapped when mem map does have hole under 4g that is found by Konard on xen domU with 8g ram. - Yinghai Signed-off-by: Jacob Shin <jacob.shin@amd.com> Link: http://lkml.kernel.org/r/1353123563-3103-16-git-send-email-yinghai@kernel.org Signed-off-by: Yinghai Lu <yinghai@kernel.org> Reviewed-by: Pekka Enberg <penberg@kernel.org> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/mm/init.c')
-rw-r--r--arch/x86/mm/init.c120
1 files changed, 109 insertions, 11 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 7b961d0b1389..bb44e9f2cc49 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -243,6 +243,38 @@ static unsigned long __init calculate_table_space_size(unsigned long start, unsi
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)
@@ -258,6 +290,34 @@ static void __init find_early_table_space(unsigned long start,
pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT);
}
+static struct range pfn_mapped[E820_X_MAX];
+static int nr_pfn_mapped;
+
+static void add_pfn_range_mapped(unsigned long start_pfn, unsigned long end_pfn)
+{
+ nr_pfn_mapped = add_range_with_merge(pfn_mapped, E820_X_MAX,
+ nr_pfn_mapped, start_pfn, end_pfn);
+ nr_pfn_mapped = clean_sort_range(pfn_mapped, E820_X_MAX);
+
+ max_pfn_mapped = max(max_pfn_mapped, end_pfn);
+
+ if (start_pfn < (1UL<<(32-PAGE_SHIFT)))
+ max_low_pfn_mapped = max(max_low_pfn_mapped,
+ min(end_pfn, 1UL<<(32-PAGE_SHIFT)));
+}
+
+bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn)
+{
+ int i;
+
+ for (i = 0; i < nr_pfn_mapped; i++)
+ if ((start_pfn >= pfn_mapped[i].start) &&
+ (end_pfn <= pfn_mapped[i].end))
+ return true;
+
+ return false;
+}
+
/*
* Setup the direct mapping of the physical memory at PAGE_OFFSET.
* This runs before bootmem is initialized and gets pages directly from
@@ -288,9 +348,55 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
__flush_tlb_all();
+ add_pfn_range_mapped(start >> PAGE_SHIFT, ret >> PAGE_SHIFT);
+
return ret >> PAGE_SHIFT;
}
+/*
+ * 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.
+ */
+static void __init init_all_memory_mapping(void)
+{
+ unsigned long start_pfn, end_pfn;
+ int i;
+
+ /* the ISA range is always mapped regardless of memory holes */
+ init_memory_mapping(0, ISA_END_ADDRESS);
+
+ for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
+ u64 start = (u64)start_pfn << PAGE_SHIFT;
+ u64 end = (u64)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
+ init_memory_mapping(start, end);
+ }
+
+#ifdef CONFIG_X86_64
+ if (max_pfn > max_low_pfn) {
+ /* can we preseve max_low_pfn ?*/
+ max_low_pfn = max_pfn;
+ }
+#endif
+}
+
void __init init_mem_mapping(void)
{
unsigned long tables, good_end, end;
@@ -311,23 +417,15 @@ void __init init_mem_mapping(void)
end = max_low_pfn << PAGE_SHIFT;
good_end = max_pfn_mapped << PAGE_SHIFT;
#endif
- tables = calculate_table_space_size(0, end);
+ 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_low_pfn_mapped = init_memory_mapping(0, max_low_pfn<<PAGE_SHIFT);
- max_pfn_mapped = max_low_pfn_mapped;
+ max_pfn_mapped = 0; /* will get exact value next */
+ init_all_memory_mapping();
-#ifdef CONFIG_X86_64
- if (max_pfn > max_low_pfn) {
- max_pfn_mapped = init_memory_mapping(1UL<<32,
- max_pfn<<PAGE_SHIFT);
- /* 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)