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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/2] xen/mm: Introduce PGC_state_uninitialised
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
It is possible for pages to enter general circulation without ever
being process by init_heap_pages().
For example, pages of the multiboot module containing the initramfs may
be assigned via assign_pages() to dom0 as it is created. And some code
including map_pages_to_xen() has checks on 'system_state' to determine
whether to use the boot or the heap allocator, but it seems impossible
to prove that pages allocated by the boot allocator are not subsequently
freed with free_heap_pages().
This actually works fine in the majority of cases; there are only a few
esoteric corner cases which init_heap_pages() handles before handing the
page range off to free_heap_pages():
• Excluding MFN #0 to avoid inappropriate cross-zone merging.
• Ensuring that the node information structures exist, when the first
page(s) of a given node are handled.
• High order allocations crossing from one node to another.
To handle this case, shift PG_state_inuse from its current value of
zero, to another value. Use zero, which is the initial state of the
entire frame table, as PG_state_uninitialised.
Fix a couple of assertions which were assuming that PG_state_inuse is
zero, and make them cope with the PG_state_uninitialised case too where
appopriate.
Finally, make free_heap_pages() call through to init_heap_pages() when
given a page range which has not been initialised. This cannot keep
recursing because init_heap_pages() will set each page state to
PGC_state_inuse before passing it back to free_heap_pages() for the
second time.
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
xen/arch/x86/mm.c | 3 ++-
xen/common/page_alloc.c | 44 +++++++++++++++++++++++++++++-----------
xen/include/asm-arm/mm.h | 3 ++-
xen/include/asm-x86/mm.h | 3 ++-
4 files changed, 38 insertions(+), 15 deletions(-)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 62507ca651..5f0581c072 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -491,7 +491,8 @@ void share_xen_page_with_guest(struct page_info *page,
struct domain *d,
page_set_owner(page, d);
smp_wmb(); /* install valid domain ptr before updating refcnt. */
- ASSERT((page->count_info & ~PGC_xen_heap) == 0);
+ ASSERT((page->count_info & ~PGC_xen_heap) == PGC_state_inuse ||
+ (page->count_info & ~PGC_xen_heap) == PGC_state_uninitialised);
/* Only add to the allocation list if the domain isn't dying. */
if ( !d->is_dying )
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 8d72a64f4e..4f7971f2a1 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -252,6 +252,8 @@ struct bootmem_region {
static struct bootmem_region __initdata
bootmem_region_list[PAGE_SIZE / sizeof(struct bootmem_region)];
static unsigned int __initdata nr_bootmem_regions;
+static void init_heap_pages(struct page_info *pg, unsigned long nr_pages,
+ bool scrub);
struct scrub_region {
unsigned long offset;
@@ -1390,6 +1392,17 @@ static void free_heap_pages(
ASSERT(order <= MAX_ORDER);
ASSERT(node >= 0);
+ if ( page_state_is(pg, uninitialised) )
+ {
+ init_heap_pages(pg, 1 << order, need_scrub);
+ /*
+ * init_heap_pages() will call back into free_heap_pages() for
+ * each page but cannot keep recursing because each page will
+ * be set to PGC_state_inuse first.
+ */
+ return;
+ }
+
spin_lock(&heap_lock);
for ( i = 0; i < (1 << order); i++ )
@@ -1771,11 +1784,10 @@ int query_page_offline(mfn_t mfn, uint32_t *status)
* latter is not on a MAX_ORDER boundary, then we reserve the page by
* not freeing it to the buddy allocator.
*/
-static void init_heap_pages(
- struct page_info *pg, unsigned long nr_pages)
+static void init_heap_pages(struct page_info *pg, unsigned long nr_pages,
+ bool scrub)
{
unsigned long i;
- bool idle_scrub = false;
/*
* Keep MFN 0 away from the buddy allocator to avoid crossing zone
@@ -1800,7 +1812,7 @@ static void init_heap_pages(
spin_unlock(&heap_lock);
if ( system_state < SYS_STATE_active && opt_bootscrub == BOOTSCRUB_IDLE )
- idle_scrub = true;
+ scrub = true;
for ( i = 0; i < nr_pages; i++ )
{
@@ -1828,7 +1840,8 @@ static void init_heap_pages(
nr_pages -= n;
}
- free_heap_pages(pg + i, 0, scrub_debug || idle_scrub);
+ pg[i].count_info = PGC_state_inuse;
+ free_heap_pages(pg + i, 0, scrub_debug || scrub);
}
}
@@ -1864,7 +1877,7 @@ void __init end_boot_allocator(void)
if ( (r->s < r->e) &&
(phys_to_nid(pfn_to_paddr(r->s)) == cpu_to_node(0)) )
{
- init_heap_pages(mfn_to_page(_mfn(r->s)), r->e - r->s);
+ init_heap_pages(mfn_to_page(_mfn(r->s)), r->e - r->s, false);
r->e = r->s;
break;
}
@@ -1873,7 +1886,7 @@ void __init end_boot_allocator(void)
{
struct bootmem_region *r = &bootmem_region_list[i];
if ( r->s < r->e )
- init_heap_pages(mfn_to_page(_mfn(r->s)), r->e - r->s);
+ init_heap_pages(mfn_to_page(_mfn(r->s)), r->e - r->s, false);
}
nr_bootmem_regions = 0;
@@ -2142,7 +2155,7 @@ void init_xenheap_pages(paddr_t ps, paddr_t pe)
memguard_guard_range(maddr_to_virt(ps), pe - ps);
- init_heap_pages(maddr_to_page(ps), (pe - ps) >> PAGE_SHIFT);
+ init_heap_pages(maddr_to_page(ps), (pe - ps) >> PAGE_SHIFT, false);
}
@@ -2251,7 +2264,7 @@ void init_domheap_pages(paddr_t ps, paddr_t pe)
if ( mfn_x(emfn) <= mfn_x(smfn) )
return;
- init_heap_pages(mfn_to_page(smfn), mfn_x(emfn) - mfn_x(smfn));
+ init_heap_pages(mfn_to_page(smfn), mfn_x(emfn) - mfn_x(smfn), false);
}
@@ -2280,7 +2293,8 @@ int assign_pages(
for ( i = 0; i < (1ul << order); i++ )
{
- ASSERT(!(pg[i].count_info & ~PGC_extra));
+ ASSERT((pg[i].count_info & ~PGC_extra) == PGC_state_inuse ||
+ (pg[i].count_info & ~PGC_extra) == PGC_state_uninitialised);
if ( pg[i].count_info & PGC_extra )
extra_pages++;
}
@@ -2316,10 +2330,16 @@ int assign_pages(
for ( i = 0; i < (1 << order); i++ )
{
ASSERT(page_get_owner(&pg[i]) == NULL);
+ /*
+ * Note: Not using page_state_is() here. The ASSERT requires that
+ * all other bits in count_info are zero, in addition to PGC_state
+ * being appropriate.
+ */
+ ASSERT((pg[i].count_info & ~PGC_extra) == PGC_state_inuse ||
+ (pg[i].count_info & ~PGC_extra) == PGC_state_uninitialised);
page_set_owner(&pg[i], d);
smp_wmb(); /* Domain pointer must be visible before updating refcnt. */
- pg[i].count_info =
- (pg[i].count_info & PGC_extra) | PGC_allocated | 1;
+ pg[i].count_info = (pg[i].count_info & PGC_state) | PGC_allocated | 1;
page_list_add_tail(&pg[i], &d->page_list);
}
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index a877791d1c..49663fa98a 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -113,12 +113,13 @@ struct page_info
* { inuse, offlining, offlined, free, broken_offlining, broken }
*/
#define PGC_state PG_mask(7, 9)
-#define PGC_state_inuse PG_mask(0, 9)
+#define PGC_state_uninitialised PG_mask(0, 9)
#define PGC_state_offlining PG_mask(1, 9)
#define PGC_state_offlined PG_mask(2, 9)
#define PGC_state_free PG_mask(3, 9)
#define PGC_state_broken_offlining PG_mask(4, 9) /* Broken and offlining */
#define PGC_state_broken PG_mask(5, 9) /* Broken and offlined */
+#define PGC_state_inuse PG_mask(6, 9)
#define pgc_is(pgc, st) (((pgc) & PGC_state) == PGC_state_##st)
#define page_state_is(pg, st) pgc_is((pg)->count_info, st)
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 1203f1b179..5fbbca5f05 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -72,12 +72,13 @@
* { inuse, offlining, offlined, free, broken_offlining, broken }
*/
#define PGC_state PG_mask(7, 9)
-#define PGC_state_inuse PG_mask(0, 9)
+#define PGC_state_uninitialised PG_mask(0, 9)
#define PGC_state_offlining PG_mask(1, 9)
#define PGC_state_offlined PG_mask(2, 9)
#define PGC_state_free PG_mask(3, 9)
#define PGC_state_broken_offlining PG_mask(4, 9) /* Broken and offlining */
#define PGC_state_broken PG_mask(5, 9) /* Broken and offlined */
+#define PGC_state_inuse PG_mask(6, 9)
#define pgc_is(pgc, st) (((pgc) & PGC_state) == PGC_state_##st)
#define page_state_is(pg, st) pgc_is((pg)->count_info, st)
--
2.21.0
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