# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Date 1174058348 0
# Node ID 3a186e94f613371b4dfa98b8e0a8d5aaf0f0d681
# Parent ba83d33c961b3e99a2d309b520162f71af56c972
linux: Various cleanup and locking clarification (and fixing!)
of mm pinning/unpinning logic.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c | 14 ++-
linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c | 98 ++++++++++++---------
2 files changed, 68 insertions(+), 44 deletions(-)
diff -r ba83d33c961b -r 3a186e94f613
linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
--- a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c Fri Mar 16 15:18:33
2007 +0000
+++ b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c Fri Mar 16 15:19:08
2007 +0000
@@ -256,8 +256,9 @@ void pte_free(struct page *pte)
unsigned long va = (unsigned long)__va(pfn << PAGE_SHIFT);
if (!pte_write(*virt_to_ptep(va)))
- BUG_ON(HYPERVISOR_update_va_mapping(
- va, pfn_pte(pfn, PAGE_KERNEL), 0));
+ if (HYPERVISOR_update_va_mapping(
+ va, pfn_pte(pfn, PAGE_KERNEL), 0))
+ BUG();
} else
clear_bit(PG_pinned, &pte->flags);
@@ -672,14 +673,23 @@ void mm_pin_all(void)
void mm_pin_all(void)
{
struct page *page;
+ unsigned long flags;
if (xen_feature(XENFEAT_writable_page_tables))
return;
+ /*
+ * Allow uninterrupted access to the pgd_list. Also protects
+ * __pgd_pin() by disabling preemption.
+ * All other CPUs must be at a safe point (e.g., in stop_machine
+ * or offlined entirely).
+ */
+ spin_lock_irqsave(&pgd_lock, flags);
for (page = pgd_list; page; page = (struct page *)page->index) {
if (!test_bit(PG_pinned, &page->flags))
__pgd_pin((pgd_t *)page_address(page));
}
+ spin_unlock_irqrestore(&pgd_lock, flags);
}
void _arch_dup_mmap(struct mm_struct *mm)
diff -r ba83d33c961b -r 3a186e94f613
linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c
--- a/linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c Fri Mar 16
15:18:33 2007 +0000
+++ b/linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c Fri Mar 16
15:19:08 2007 +0000
@@ -79,14 +79,17 @@ void mm_pin(struct mm_struct *mm)
spin_lock(&mm->page_table_lock);
mm_walk(mm, PAGE_KERNEL_RO);
- BUG_ON(HYPERVISOR_update_va_mapping(
- (unsigned long)mm->pgd,
- pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT,
PAGE_KERNEL_RO),
- UVMF_TLB_FLUSH));
- BUG_ON(HYPERVISOR_update_va_mapping(
- (unsigned long)__user_pgd(mm->pgd),
- pfn_pte(virt_to_phys(__user_pgd(mm->pgd))>>PAGE_SHIFT,
PAGE_KERNEL_RO),
- UVMF_TLB_FLUSH));
+ if (HYPERVISOR_update_va_mapping(
+ (unsigned long)mm->pgd,
+ pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL_RO),
+ UVMF_TLB_FLUSH))
+ BUG();
+ if (HYPERVISOR_update_va_mapping(
+ (unsigned long)__user_pgd(mm->pgd),
+ pfn_pte(virt_to_phys(__user_pgd(mm->pgd))>>PAGE_SHIFT,
+ PAGE_KERNEL_RO),
+ UVMF_TLB_FLUSH))
+ BUG();
xen_pgd_pin(__pa(mm->pgd)); /* kernel */
xen_pgd_pin(__pa(__user_pgd(mm->pgd))); /* user */
mm->context.pinned = 1;
@@ -106,12 +109,15 @@ void mm_unpin(struct mm_struct *mm)
xen_pgd_unpin(__pa(mm->pgd));
xen_pgd_unpin(__pa(__user_pgd(mm->pgd)));
- BUG_ON(HYPERVISOR_update_va_mapping(
- (unsigned long)mm->pgd,
- pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL),
0));
- BUG_ON(HYPERVISOR_update_va_mapping(
- (unsigned long)__user_pgd(mm->pgd),
- pfn_pte(virt_to_phys(__user_pgd(mm->pgd))>>PAGE_SHIFT,
PAGE_KERNEL), 0));
+ if (HYPERVISOR_update_va_mapping(
+ (unsigned long)mm->pgd,
+ pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL), 0))
+ BUG();
+ if (HYPERVISOR_update_va_mapping(
+ (unsigned long)__user_pgd(mm->pgd),
+ pfn_pte(virt_to_phys(__user_pgd(mm->pgd))>>PAGE_SHIFT,
+ PAGE_KERNEL), 0))
+ BUG();
mm_walk(mm, PAGE_KERNEL);
xen_tlb_flush();
mm->context.pinned = 0;
@@ -127,43 +133,50 @@ void mm_pin_all(void)
if (xen_feature(XENFEAT_writable_page_tables))
return;
+ /*
+ * Allow uninterrupted access to the mm_unpinned list. We don't
+ * actually take the mm_unpinned_lock as it is taken inside mm_pin().
+ * All other CPUs must be at a safe point (e.g., in stop_machine
+ * or offlined entirely).
+ */
+ preempt_disable();
while (!list_empty(&mm_unpinned))
mm_pin(list_entry(mm_unpinned.next, struct mm_struct,
context.unpinned));
+ preempt_enable();
}
void _arch_dup_mmap(struct mm_struct *mm)
{
- if (!mm->context.pinned)
- mm_pin(mm);
+ if (!mm->context.pinned)
+ mm_pin(mm);
}
void _arch_exit_mmap(struct mm_struct *mm)
{
- struct task_struct *tsk = current;
-
- task_lock(tsk);
-
- /*
- * We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
- * *much* faster this way, as no tlb flushes means bigger wrpt batches.
- */
- if ( tsk->active_mm == mm )
- {
- tsk->active_mm = &init_mm;
- atomic_inc(&init_mm.mm_count);
-
- switch_mm(mm, &init_mm, tsk);
-
- atomic_dec(&mm->mm_count);
- BUG_ON(atomic_read(&mm->mm_count) == 0);
- }
-
- task_unlock(tsk);
-
- if ( mm->context.pinned && (atomic_read(&mm->mm_count) == 1) &&
- !mm->context.has_foreign_mappings )
- mm_unpin(mm);
+ struct task_struct *tsk = current;
+
+ task_lock(tsk);
+
+ /*
+ * We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
+ * *much* faster this way, as no tlb flushes means bigger wrpt batches.
+ */
+ if (tsk->active_mm == mm) {
+ tsk->active_mm = &init_mm;
+ atomic_inc(&init_mm.mm_count);
+
+ switch_mm(mm, &init_mm, tsk);
+
+ atomic_dec(&mm->mm_count);
+ BUG_ON(atomic_read(&mm->mm_count) == 0);
+ }
+
+ task_unlock(tsk);
+
+ if ( mm->context.pinned && (atomic_read(&mm->mm_count) == 1) &&
+ !mm->context.has_foreign_mappings )
+ mm_unpin(mm);
}
struct page *pte_alloc_one(struct mm_struct *mm, unsigned long address)
@@ -183,8 +196,9 @@ void pte_free(struct page *pte)
unsigned long va = (unsigned long)__va(page_to_pfn(pte)<<PAGE_SHIFT);
if (!pte_write(*virt_to_ptep(va)))
- BUG_ON(HYPERVISOR_update_va_mapping(
- va, pfn_pte(page_to_pfn(pte), PAGE_KERNEL), 0));
+ if (HYPERVISOR_update_va_mapping(
+ va, pfn_pte(page_to_pfn(pte), PAGE_KERNEL), 0))
+ BUG();
ClearPageForeign(pte);
init_page_count(pte);
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