[PATCH 2/2] x86,mem-hotplug: modify PGD entry when removing memory
From: Yasuaki Ishimatsu
Date: Wed Jun 18 2014 - 02:41:53 EST
When hot-adding/removing memory, sync_global_pgds() is called for
synchronizing PGD to PGD entries of all processes MM. But when
hot-removing memory, sync_global_pgds() does not work correctly.
At first, sync_global_pgds() checks whether target PGD is none or not.
And if PGD is none, the PGD is skipped. But when hot-removing memory,
PGD may be none since PGD may be cleared by free_pud_table(). So
when sync_global_pgds() is called after hot-removing memory,
sync_global_pgds() should not skip PGD even if the PGD is none.
And sync_global_pgds() must clear PGD entries of all processes MM.
Currently sync_global_pgds() does not clear PGD entries of all processes
MM when hot-removing memory. So when hot adding memory which is same memory
range as removed memory after hot-removing memory, following call traces
are shown:
kernel BUG at arch/x86/mm/init_64.c:206!
...
[<ffffffff815e0c80>] kernel_physical_mapping_init+0x1b2/0x1d2
[<ffffffff815ced94>] init_memory_mapping+0x1d4/0x380
[<ffffffff8104aebd>] arch_add_memory+0x3d/0xd0
[<ffffffff815d03d9>] add_memory+0xb9/0x1b0
[<ffffffff81352415>] acpi_memory_device_add+0x1af/0x28e
[<ffffffff81325dc4>] acpi_bus_device_attach+0x8c/0xf0
[<ffffffff813413b9>] acpi_ns_walk_namespace+0xc8/0x17f
[<ffffffff81325d38>] ? acpi_bus_type_and_status+0xb7/0xb7
[<ffffffff81325d38>] ? acpi_bus_type_and_status+0xb7/0xb7
[<ffffffff813418ed>] acpi_walk_namespace+0x95/0xc5
[<ffffffff81326b4c>] acpi_bus_scan+0x9a/0xc2
[<ffffffff81326bff>] acpi_scan_bus_device_check+0x8b/0x12e
[<ffffffff81326cb5>] acpi_scan_device_check+0x13/0x15
[<ffffffff81320122>] acpi_os_execute_deferred+0x25/0x32
[<ffffffff8107e02b>] process_one_work+0x17b/0x460
[<ffffffff8107edfb>] worker_thread+0x11b/0x400
[<ffffffff8107ece0>] ? rescuer_thread+0x400/0x400
[<ffffffff81085aef>] kthread+0xcf/0xe0
[<ffffffff81085a20>] ? kthread_create_on_node+0x140/0x140
[<ffffffff815fc76c>] ret_from_fork+0x7c/0xb0
[<ffffffff81085a20>] ? kthread_create_on_node+0x140/0x140
This patch clears PGD entries of all processes MM when sync_global_pgds()
is called after hot-removing memory
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
---
arch/x86/include/asm/pgtable_64.h | 3 ++-
arch/x86/mm/fault.c | 2 +-
arch/x86/mm/init_64.c | 27 +++++++++++++++++++--------
3 files changed, 22 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 5be9063..809abb3 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -115,7 +115,8 @@ static inline void native_pgd_clear(pgd_t *pgd)
native_set_pgd(pgd, native_make_pgd(0));
}
-extern void sync_global_pgds(unsigned long start, unsigned long end);
+extern void sync_global_pgds(unsigned long start, unsigned long end,
+ int removed);
/*
* Conversion functions: convert a page and protection to a page entry,
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 3664279..0193a32 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -350,7 +350,7 @@ out:
void vmalloc_sync_all(void)
{
- sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
+ sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END, 0);
}
/*
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a5b245d..8f68032 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -178,7 +178,7 @@ __setup("noexec32=", nonx32_setup);
* When memory was added/removed make sure all the processes MM have
* suitable PGD entries in the local PGD level page.
*/
-void sync_global_pgds(unsigned long start, unsigned long end)
+void sync_global_pgds(unsigned long start, unsigned long end, int removed)
{
unsigned long address;
@@ -186,7 +186,12 @@ void sync_global_pgds(unsigned long start, unsigned long end)
const pgd_t *pgd_ref = pgd_offset_k(address);
struct page *page;
- if (pgd_none(*pgd_ref))
+ /*
+ * When it is called after memory hot remove, pgd_none()
+ * returns true. In this case (removed == 1), we must clear
+ * the PGD entries in the local PGD level page.
+ */
+ if (pgd_none(*pgd_ref) && !removed)
continue;
spin_lock(&pgd_lock);
@@ -199,12 +204,18 @@ void sync_global_pgds(unsigned long start, unsigned long end)
pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
spin_lock(pgt_lock);
- if (pgd_none(*pgd))
- set_pgd(pgd, *pgd_ref);
- else
+ if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
BUG_ON(pgd_page_vaddr(*pgd)
!= pgd_page_vaddr(*pgd_ref));
+ if (removed) {
+ if (pgd_none(*pgd_ref) && !pgd_none(*pgd))
+ pgd_clear(pgd);
+ } else {
+ if (pgd_none(*pgd))
+ set_pgd(pgd, *pgd_ref);
+ }
+
spin_unlock(pgt_lock);
}
spin_unlock(&pgd_lock);
@@ -633,7 +644,7 @@ kernel_physical_mapping_init(unsigned long start,
}
if (pgd_changed)
- sync_global_pgds(addr, end - 1);
+ sync_global_pgds(addr, end - 1, 0);
__flush_tlb_all();
@@ -994,7 +1005,7 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct)
}
if (pgd_changed)
- sync_global_pgds(start, end - 1);
+ sync_global_pgds(start, end - 1, 1);
flush_tlb_all();
}
@@ -1341,7 +1352,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
else
err = vmemmap_populate_basepages(start, end, node);
if (!err)
- sync_global_pgds(start, end - 1);
+ sync_global_pgds(start, end - 1, 0);
return err;
}
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