xen/balloon: don't alloc page while non-preemptible
get_balloon_scratch_page() disables preemption so we cannot call
alloc_page() in between get/put_balloon_scratch_page(). Shuffle bits
around in decrease_reservation() to avoid this.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index a50c6e3..b232908 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -398,8 +398,6 @@
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
- scratch_page = get_balloon_scratch_page();
-
for (i = 0; i < nr_pages; i++) {
page = alloc_page(gfp);
if (page == NULL) {
@@ -413,6 +411,12 @@
scrub_page(page);
+ /*
+ * Ballooned out frames are effectively replaced with
+ * a scratch frame. Ensure direct mappings and the
+ * p2m are consistent.
+ */
+ scratch_page = get_balloon_scratch_page();
#ifdef CONFIG_XEN_HAVE_PVMMU
if (xen_pv_domain() && !PageHighMem(page)) {
ret = HYPERVISOR_update_va_mapping(
@@ -422,24 +426,19 @@
BUG_ON(ret);
}
#endif
- }
-
- /* Ensure that ballooned highmem pages don't have kmaps. */
- kmap_flush_unused();
- flush_tlb_all();
-
- /* No more mappings: invalidate P2M and add to balloon. */
- for (i = 0; i < nr_pages; i++) {
- pfn = mfn_to_pfn(frame_list[i]);
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long p;
p = page_to_pfn(scratch_page);
__set_phys_to_machine(pfn, pfn_to_mfn(p));
}
+ put_balloon_scratch_page();
+
balloon_append(pfn_to_page(pfn));
}
- put_balloon_scratch_page();
+ /* Ensure that ballooned highmem pages don't have kmaps. */
+ kmap_flush_unused();
+ flush_tlb_all();
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;