[PATCH v1] xen/balloon: Set pages PageOffline() in balloon_add_region()

[PATCH v1] xen/balloon: Set pages PageOffline() in balloon_add_region()

[David Hildenbrand]

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);
 		__balloon_append(page);
 	}
 
-- 
2.21.0

Re: [PATCH v1] xen/balloon: Set pages PageOffline() in balloon_add_region()

[Boris Ostrovsky]

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);
>  		__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().

-boris

Re: [PATCH v1] xen/balloon: Set pages PageOffline() in balloon_add_region()

[David Hildenbrand]

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);
>>  		__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