# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1206978304 -3600
# Node ID d0b9857ea5922a7b213c316daa23acb3c7cdae33
# Parent 1866bf67b39cbedc53f9462f82459cec8d31c0a4
xen: fix grant table bug
A PV OS has two grant table data structures: the grant table itself
and a free list. The free list is composed of an array of pages,
which grow dynamically as the guest OS requires more grants. While
the grant table contains 8-byte entries, the free list contains 4-byte
entries. So we have half as many pages in the free list than in the
grant table.
There was a bug in the free list allocation code. The free list was
indexed as if it was the same size as the grant table. But it's only
half as large. So memory got corrupted, and I was seeing crashes in
the slab allocator later on.
Signed-off-by: Michael Abd-El-Malek <mabdelmalek@xxxxxxx>
linux-2.6.18-xen changeset: 502:4018c0da336008e5dfb1163bddbdfbc328c8f5c4
linux-2.6.18-xen date: Mon Mar 31 11:03:07 2008 +0100
---
linux-2.6-xen-sparse/drivers/xen/core/gnttab.c | 39 +++++++++++++------------
1 files changed, 21 insertions(+), 18 deletions(-)
diff -r 1866bf67b39c -r d0b9857ea592
linux-2.6-xen-sparse/drivers/xen/core/gnttab.c
--- a/linux-2.6-xen-sparse/drivers/xen/core/gnttab.c Mon Mar 31 16:44:42
2008 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/core/gnttab.c Mon Mar 31 16:45:04
2008 +0100
@@ -50,7 +50,7 @@
/* External tools reserve first few grant table entries. */
#define NR_RESERVED_ENTRIES 8
#define GNTTAB_LIST_END 0xffffffff
-#define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(grant_entry_t))
+#define ENTRIES_PER_GRANT_FRAME (PAGE_SIZE / sizeof(grant_entry_t))
static grant_ref_t **gnttab_list;
static unsigned int nr_grant_frames;
@@ -67,6 +67,9 @@ static int gnttab_expand(unsigned int re
#define RPP (PAGE_SIZE / sizeof(grant_ref_t))
#define gnttab_entry(entry) (gnttab_list[(entry) / RPP][(entry) % RPP])
+
+#define nr_freelist_frames(grant_frames) \
+ (((grant_frames) * ENTRIES_PER_GRANT_FRAME + RPP - 1) / RPP)
static int get_free_entries(int count)
{
@@ -369,24 +372,25 @@ static int grow_gnttab_list(unsigned int
static int grow_gnttab_list(unsigned int more_frames)
{
unsigned int new_nr_grant_frames, extra_entries, i;
+ unsigned int nr_glist_frames, new_nr_glist_frames;
new_nr_grant_frames = nr_grant_frames + more_frames;
- extra_entries = more_frames * GREFS_PER_GRANT_FRAME;
-
- for (i = nr_grant_frames; i < new_nr_grant_frames; i++)
- {
+ extra_entries = more_frames * ENTRIES_PER_GRANT_FRAME;
+
+ nr_glist_frames = nr_freelist_frames(nr_grant_frames);
+ new_nr_glist_frames = nr_freelist_frames(new_nr_grant_frames);
+ for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
if (!gnttab_list[i])
goto grow_nomem;
}
-
- for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames;
- i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
+ for (i = ENTRIES_PER_GRANT_FRAME * nr_grant_frames;
+ i < ENTRIES_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
gnttab_entry(i) = i + 1;
gnttab_entry(i) = gnttab_free_head;
- gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames;
+ gnttab_free_head = ENTRIES_PER_GRANT_FRAME * nr_grant_frames;
gnttab_free_count += extra_entries;
nr_grant_frames = new_nr_grant_frames;
@@ -396,7 +400,7 @@ static int grow_gnttab_list(unsigned int
return 0;
grow_nomem:
- for ( ; i >= nr_grant_frames; i--)
+ for ( ; i >= nr_glist_frames; i--)
free_page((unsigned long) gnttab_list[i]);
return -ENOMEM;
}
@@ -564,8 +568,8 @@ static int gnttab_expand(unsigned int re
unsigned int cur, extra;
cur = nr_grant_frames;
- extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /
- GREFS_PER_GRANT_FRAME);
+ extra = ((req_entries + (ENTRIES_PER_GRANT_FRAME-1)) /
+ ENTRIES_PER_GRANT_FRAME);
if (cur + extra > max_nr_grant_frames())
return -ENOSPC;
@@ -578,7 +582,7 @@ int __devinit gnttab_init(void)
int __devinit gnttab_init(void)
{
int i;
- unsigned int max_nr_glist_frames;
+ unsigned int max_nr_glist_frames, nr_glist_frames;
unsigned int nr_init_grefs;
if (!is_running_on_xen())
@@ -590,16 +594,15 @@ int __devinit gnttab_init(void)
/* Determine the maximum number of frames required for the
* grant reference free list on the current hypervisor.
*/
- max_nr_glist_frames = (boot_max_nr_grant_frames *
- GREFS_PER_GRANT_FRAME /
- (PAGE_SIZE / sizeof(grant_ref_t)));
+ max_nr_glist_frames = nr_freelist_frames(boot_max_nr_grant_frames);
gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
GFP_KERNEL);
if (gnttab_list == NULL)
return -ENOMEM;
- for (i = 0; i < nr_grant_frames; i++) {
+ nr_glist_frames = nr_freelist_frames(nr_grant_frames);
+ for (i = 0; i < nr_glist_frames; i++) {
gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
if (gnttab_list[i] == NULL)
goto ini_nomem;
@@ -608,7 +611,7 @@ int __devinit gnttab_init(void)
if (gnttab_resume() < 0)
return -ENODEV;
- nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME;
+ nr_init_grefs = nr_grant_frames * ENTRIES_PER_GRANT_FRAME;
for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
gnttab_entry(i) = i + 1;
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