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@xxxxxxxxxxxxxxxxxxxxxx>
>> Tested-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
>> Fixes: 77c4adf6a6df ("xen/balloon: mark inflated pages PG_offline")
>> Cc: stable@xxxxxxxxxxxxxxx # v5.1+
>> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
>> Cc: Juergen Gross <jgross@xxxxxxxx>
>> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>> ---
>> 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);
>> __balloon_append(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).
--
Thanks,
David / dhildenb
