On 27.09.19 20:08, Boris Ostrovsky wrote:
On 9/27/19 11:46 AM, David Hildenbrand wrote:
We are missing a __SetPageOffline(), which is why we can get !PageOffline() pages onto the balloon list, where alloc_xenballooned_pages() will complain:
page:ffffea0003e7ffc0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0xffffe00001000(reserved) raw: 000ffffe00001000 dead000000000100 dead000000000200 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 page dumped because: VM_BUG_ON_PAGE(!PageOffline(page)) ------------[ cut here ]------------ kernel BUG at include/linux/page-flags.h:744! invalid opcode: 0000 [#1] SMP NOPTI
Reported-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Tested-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Fixes: 77c4adf6a6df ("xen/balloon: mark inflated pages PG_offline") Cc: stable@vger.kernel.org # v5.1+ Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Juergen Gross jgross@suse.com Cc: Stefano Stabellini sstabellini@kernel.org Signed-off-by: David Hildenbrand david@redhat.com
drivers/xen/balloon.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 05b1f7e948ef..29f6256363db 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -687,6 +687,7 @@ static void __init balloon_add_region(unsigned long start_pfn, /* totalram_pages and totalhigh_pages do not include the boot-time balloon extension, so don't subtract from it. */
__SetPageOffline(page);Given that when a page is appended to balloon list need to be marked offline and, conversely, when a page is retrieved the bit should be cleared I wonder whether it's better to move Set/ClearPageOffline to balloon_append/retrieve().
Yes, we can do that as an addon patch (and also get rid of either __balloon_append() or balloon_append() if I remember correctly).