On 9/6/2013 11:09 AM, Stefano Stabellini wrote:
On Fri, 6 Sep 2013, Boris Ostrovsky wrote:
m2p_remove_override() calls get_balloon_scratch_page() in
MULTI_update_va_mapping() even though it already has pointer to this page from
the earlier call (in scratch_page). This second call doesn't have a matching
put_balloon_scratch_page() thus not restoring preempt count back. (Also, there
is no put_balloon_scratch_page() in the error path.)
In addition, the second multicall uses __xen_mc_entry() which does not disable
interrupts. Rearrange xen_mc_* calls to keep interrupts off while performing
multicalls.
Signed-off-by: Boris Ostrovsky <[email protected]>
You also might want to mention that this fixes the regression introduced
by ..
commit id <"title"
Reviewed-by: Stefano Stabellini <[email protected]>
arch/x86/xen/p2m.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 0d4ec35..8b901e8 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -990,10 +990,13 @@ int m2p_remove_override(struct page *page,
printk(KERN_WARNING "m2p_remove_override: "
"pfn %lx mfn %lx, failed to modify
kernel mappings",
pfn, mfn);
+ put_balloon_scratch_page();
return -1;
}
- mcs = xen_mc_entry(
+ xen_mc_batch();
+
+ mcs = __xen_mc_entry(
sizeof(struct
gnttab_unmap_and_replace));
unmap_op = mcs.args;
unmap_op->host_addr = kmap_op->host_addr;
@@ -1003,12 +1006,11 @@ int m2p_remove_override(struct page *page,
MULTI_grant_table_op(mcs.mc,
GNTTABOP_unmap_and_replace, unmap_op,
1);
- xen_mc_issue(PARAVIRT_LAZY_MMU);
-
mcs = __xen_mc_entry(0);
MULTI_update_va_mapping(mcs.mc, scratch_page_address,
-
pfn_pte(page_to_pfn(get_balloon_scratch_page()),
+ pfn_pte(page_to_pfn(scratch_page),
PAGE_KERNEL_RO), 0);
+
xen_mc_issue(PARAVIRT_LAZY_MMU);
kmap_op->host_addr = 0;
--
1.8.3.1
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