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| author | Wei Liu <wei.liu2@citrix.com> | 2014-03-15 16:11:47 +0000 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-04-03 10:32:25 +0200 |
| commit | d9533eb760138b04989cd6ff64121cf45f8a6636 (patch) | |
| tree | ff53b4024cc46afe54263256aa8286a75442bac3 /drivers/xen | |
| parent | 6ed1a01c0d5512d66c04326cd4963ee1d871fa9c (diff) | |
| download | lwn-d9533eb760138b04989cd6ff64121cf45f8a6636.tar.gz lwn-d9533eb760138b04989cd6ff64121cf45f8a6636.zip | |
xen/balloon: flush persistent kmaps in correct position
commit 09ed3d5ba06137913960f9c9385f71fc384193ab upstream.
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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'drivers/xen')
| -rw-r--r-- | drivers/xen/balloon.c | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index b232908a6192..4c437efa9d91 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -405,11 +405,25 @@ 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); /* * Ballooned out frames are effectively replaced with @@ -433,11 +447,9 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) } put_balloon_scratch_page(); - 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); |