# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Node ID 3e39cc16dd4164c7b5debb6649e6531cf8d9fd22
# Parent 596b0e4fbef4069bfb3ee9807f2ccfdd65052c46
[XEN] Clean up mark_dirty() usage in mm.c some more.
Add clarifying comments. Move mark_dirty() in alloc_page_type()
to end of the function (more correct).
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
xen/arch/x86/mm.c | 51 +++++++++++++++++++++++++------------------
xen/include/asm-x86/shadow.h | 13 +++++++---
2 files changed, 39 insertions(+), 25 deletions(-)
diff -r 596b0e4fbef4 -r 3e39cc16dd41 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Wed Sep 20 16:52:15 2006 +0100
+++ b/xen/arch/x86/mm.c Wed Sep 20 17:58:10 2006 +0100
@@ -1490,24 +1490,26 @@ static int mod_l4_entry(l4_pgentry_t *pl
int alloc_page_type(struct page_info *page, unsigned long type)
{
- struct domain *owner = page_get_owner(page);
-
- if ( owner != NULL )
- mark_dirty(owner, page_to_mfn(page));
+ int rc;
switch ( type & PGT_type_mask )
{
case PGT_l1_page_table:
- return alloc_l1_table(page);
+ rc = alloc_l1_table(page);
+ break;
case PGT_l2_page_table:
- return alloc_l2_table(page, type);
+ rc = alloc_l2_table(page, type);
+ break;
case PGT_l3_page_table:
- return alloc_l3_table(page);
+ rc = alloc_l3_table(page);
+ break;
case PGT_l4_page_table:
- return alloc_l4_table(page);
+ rc = alloc_l4_table(page);
+ break;
case PGT_gdt_page:
case PGT_ldt_page:
- return alloc_segdesc_page(page);
+ rc = alloc_segdesc_page(page);
+ break;
default:
printk("Bad type in alloc_page_type %lx t=%" PRtype_info " c=%x\n",
type, page->u.inuse.type_info,
@@ -1515,7 +1517,15 @@ int alloc_page_type(struct page_info *pa
BUG();
}
- return 0;
+ /*
+ * A page is dirtied when its type count becomes non-zero.
+ * It is safe to mark dirty here because any PTE modifications in
+ * alloc_l?_table have now happened. The caller has already set the type
+ * and incremented the reference count.
+ */
+ mark_dirty(page_get_owner(page), page_to_mfn(page));
+
+ return rc;
}
@@ -1615,16 +1625,13 @@ void put_page_type(struct page_info *pag
}
while ( unlikely((y = cmpxchg(&page->u.inuse.type_info, x, nx)) != x) );
- if( likely(owner != NULL) )
- {
- if (shadow_mode_enabled(owner))
- {
- if (shadow_lock_is_acquired(owner)) /* this is a shadow page */
- return;
-
- mark_dirty(owner, page_to_mfn(page));
- }
- }
+ /*
+ * A page is dirtied when its type count becomes zero.
+ * We cannot set the dirty flag earlier than this because we must wait
+ * until the type count has been zeroed by the CMPXCHG above.
+ */
+ if ( unlikely((nx & PGT_count_mask) == 0) )
+ mark_dirty(owner, page_to_mfn(page));
}
@@ -1984,6 +1991,7 @@ int do_mmuext_op(
break;
}
+ /* A page is dirtied when its pin status is set. */
mark_dirty(d, mfn);
break;
@@ -2006,8 +2014,9 @@ int do_mmuext_op(
{
shadow_lock(d);
shadow_remove_all_shadows(v, _mfn(mfn));
+ /* A page is dirtied when its pin status is cleared. */
+ sh_mark_dirty(d, _mfn(mfn));
shadow_unlock(d);
- mark_dirty(d, mfn);
}
}
else
diff -r 596b0e4fbef4 -r 3e39cc16dd41 xen/include/asm-x86/shadow.h
--- a/xen/include/asm-x86/shadow.h Wed Sep 20 16:52:15 2006 +0100
+++ b/xen/include/asm-x86/shadow.h Wed Sep 20 17:58:10 2006 +0100
@@ -325,12 +325,17 @@ void sh_do_mark_dirty(struct domain *d,
void sh_do_mark_dirty(struct domain *d, mfn_t gmfn);
static inline void mark_dirty(struct domain *d, unsigned long gmfn)
{
- if ( shadow_mode_log_dirty(d) )
- {
+ int caller_locked;
+
+ if ( unlikely(d == NULL) || likely(!shadow_mode_log_dirty(d)) )
+ return;
+
+ caller_locked = shadow_lock_is_acquired(d);
+ if ( !caller_locked )
shadow_lock(d);
- sh_do_mark_dirty(d, _mfn(gmfn));
+ sh_do_mark_dirty(d, _mfn(gmfn));
+ if ( !caller_locked )
shadow_unlock(d);
- }
}
/* Internal version, for when the shadow lock is already held */
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