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authorWei Liu <wei.liu2@citrix.com>2014-03-15 16:11:47 +0000
committerDavid Vrabel <david.vrabel@citrix.com>2014-03-25 10:38:30 +0000
commit09ed3d5ba06137913960f9c9385f71fc384193ab (patch)
tree582150ce743efb10051e0bc13747e3e1a24005b9 /drivers
parentb098d6726bbfb94c06d6e1097466187afddae61f (diff)
downloadlinux-linaro-stable-09ed3d5ba06137913960f9c9385f71fc384193ab.tar.gz
xen/balloon: flush persistent kmaps in correct position
Xen balloon driver will update ballooned out pages' P2M entries to point to scratch page for PV guests. In 24f69373e2 ("xen/balloon: don't alloc page while non-preemptible", kmap_flush_unused was moved after updating P2M table. In that case for 32 bit PV guest we might end up with P2M X -----> S (S is mfn of balloon scratch page) M2P Y -----> X (Y is mfn in persistent kmap entry) kmap_flush_unused() iterates through all the PTEs in the kmap address space, using pte_to_page() to obtain the page. If the p2m and the m2p are inconsistent the incorrect page is returned. This will clear page->address on the wrong page which may cause subsequent oopses if that page is currently kmap'ed. Move the flush back between get_page and __set_phys_to_machine to fix this. Signed-off-by: Wei Liu <wei.liu2@citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Cc: stable@vger.kernel.org # 3.12+
Diffstat (limited to 'drivers')
-rw-r--r--drivers/xen/balloon.c24
1 files changed, 18 insertions, 6 deletions
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 37d06ea624aa..61a6ac8fa8fc 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -399,11 +399,25 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
state = BP_EAGAIN;
break;
}
+ scrub_page(page);
- pfn = page_to_pfn(page);
- frame_list[i] = pfn_to_mfn(pfn);
+ frame_list[i] = page_to_pfn(page);
+ }
- scrub_page(page);
+ /*
+ * Ensure that ballooned highmem pages don't have kmaps.
+ *
+ * Do this before changing the p2m as kmap_flush_unused()
+ * reads PTEs to obtain pages (and hence needs the original
+ * p2m entry).
+ */
+ kmap_flush_unused();
+
+ /* Update direct mapping, invalidate P2M, and add to balloon. */
+ for (i = 0; i < nr_pages; i++) {
+ pfn = frame_list[i];
+ frame_list[i] = pfn_to_mfn(pfn);
+ page = pfn_to_page(pfn);
#ifdef CONFIG_XEN_HAVE_PVMMU
/*
@@ -429,11 +443,9 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
}
#endif
- balloon_append(pfn_to_page(pfn));
+ balloon_append(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);