Re: [Qemu-devel] [PATCH 5/5] balloon: Use only 'pc-dimm' type dimm for ballooning

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

On 05.02.2016 15:58, Igor Mammedov wrote:
> On Fri,  5 Feb 2016 11:19:01 +0300
> Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> wrote:
>
>> For now there are only two dimm's: pc-dimm and nvdimm. This patch is
>> actually needed to disable ballooning on nvdimm. But, to avoid future
>> bugs, instead of disallowing nvdimm, we allow only pc-dimm. So, if
>> someone adds new dimm which should be balloon-able, then this ability
>> should be explicitly specified here.
>>
>> Why ballooning for nvdimm should be disabled for now:
>>
>> NVDIMM for now is planned to use as a backing store for DAX filesystem
>> in the guest and thus this memory is excluded from guest memory
>> management and LRUs.
>>
>> In this case libvirt running QEMU along with configured balloon almost
>> immediately inflates balloon and effectively kill the guest as
>> qemu counts nvdimm as part of the ram.
>>
>> Counting dimm devices as part of the ram for ballooning was started from
>> commit 463756d03:
>>   virtio-balloon: Fix balloon not working correctly when hotplug memory
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> ---
>>   hw/virtio/virtio-balloon.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
>> index b9c1964..0415e07 100644
>> --- a/hw/virtio/virtio-balloon.c
>> +++ b/hw/virtio/virtio-balloon.c
>> @@ -18,6 +18,7 @@
>>   #include "qemu-common.h"
>>   #include "hw/virtio/virtio.h"
>>   #include "hw/i386/pc.h"
>> +#include "hw/mem/nvdimm.h"
> Is this include still needed?

Yes, for TYPE_PC_DIMM

>
>>   #include "cpu.h"
>>   #include "sysemu/balloon.h"
>>   #include "hw/virtio/virtio-balloon.h"
>> @@ -302,7 +303,10 @@ static ram_addr_t get_current_ram_size(void)
>>       pc_dimm_build_list(qdev_get_machine(), &list);
>>       for (item = list; item; item = g_slist_next(item)) {
>>           PCDIMMDevice *dimm = item->data;
>> -        size += object_property_get_int(OBJECT(dimm), PC_DIMM_SIZE_PROP, NULL);
>> +        if (!strcmp(object_get_typename(OBJECT(dimm)), TYPE_PC_DIMM)) {
>> +            size += object_property_get_int(OBJECT(dimm), PC_DIMM_SIZE_PROP,
>> +                                            NULL);
>> +        }
>>       }
>>       g_slist_free(list);
>>   


-- 
Best regards,
Vladimir