Linux Virtualization - Dec 2018 - [PATCH v37 1/3] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT

On 27.08.2018 03:32, Wei Wang wrote:
>  static int init_vqs(struct virtio_balloon *vb)
>  {
> -	struct virtqueue *vqs[3];
> -	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
> -	static const char * const names[] = { "inflate",
"deflate", "stats" };
> -	int err, nvqs;
> +	struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
> +	vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
> +	const char *names[VIRTIO_BALLOON_VQ_MAX];
> +	int err;
> 
>  	/*
> -	 * We expect two virtqueues: inflate and deflate, and
> -	 * optionally stat.
> +	 * Inflateq and deflateq are used unconditionally. The names[]
> +	 * will be NULL if the related feature is not enabled, which will
> +	 * cause no allocation for the corresponding virtqueue in find_vqs.
>  	 */
This might be true for virtio-pci, but it is not for virtio-ccw.
> -	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 :
2;
> -	err = virtio_find_vqs(vb->vdev, nvqs, vqs, callbacks, names, NULL);
> +	callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
> +	names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
> +	callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
> +	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
> +	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
> +	names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
> +
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> +		names[VIRTIO_BALLOON_VQ_STATS] = "stats";
> +		callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
> +	}
> +
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
> +		names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
> +		callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
> +	}
> +
> +	err = vb->vdev->config->find_vqs(vb->vdev,
VIRTIO_BALLOON_VQ_MAX,
[...]

On 12/27/2018 08:03 PM, Christian Borntraeger wrote:
> On 27.08.2018 03:32, Wei Wang wrote:
>>   static int init_vqs(struct virtio_balloon *vb)
>>   {
>> -	struct virtqueue *vqs[3];
>> -	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack,
stats_request };
>> -	static const char * const names[] = { "inflate",
"deflate", "stats" };
>> -	int err, nvqs;
>> +	struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
>> +	vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
>> +	const char *names[VIRTIO_BALLOON_VQ_MAX];
>> +	int err;
>>
>>   	/*
>> -	 * We expect two virtqueues: inflate and deflate, and
>> -	 * optionally stat.
>> +	 * Inflateq and deflateq are used unconditionally. The names[]
>> +	 * will be NULL if the related feature is not enabled, which will
>> +	 * cause no allocation for the corresponding virtqueue in find_vqs.
>>   	 */
> This might be true for virtio-pci, but it is not for virtio-ccw.
Hi Christian,


Please try the fix patches: https://lkml.org/lkml/2018/12/27/336

Best,
Wei

On 28.12.2018 04:12, Wei Wang wrote:
> On 12/27/2018 08:03 PM, Christian Borntraeger wrote:
>> On 27.08.2018 03:32, Wei Wang wrote:
>>> ? static int init_vqs(struct virtio_balloon *vb)
>>> ? {
>>> -??? struct virtqueue *vqs[3];
>>> -??? vq_callback_t *callbacks[] = { balloon_ack, balloon_ack,
stats_request };
>>> -??? static const char * const names[] = { "inflate",
"deflate", "stats" };
>>> -??? int err, nvqs;
>>> +??? struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
>>> +??? vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
>>> +??? const char *names[VIRTIO_BALLOON_VQ_MAX];
>>> +??? int err;
>>>
>>> ????? /*
>>> -???? * We expect two virtqueues: inflate and deflate, and
>>> -???? * optionally stat.
>>> +???? * Inflateq and deflateq are used unconditionally. The names[]
>>> +???? * will be NULL if the related feature is not enabled, which
will
>>> +???? * cause no allocation for the corresponding virtqueue in
find_vqs.
>>> ?????? */
>> This might be true for virtio-pci, but it is not for virtio-ccw.
> 
> Hi Christian,
> 
> 
> Please try the fix patches: https://lkml.org/lkml/2018/12/27/336
See answer to that thread. It fixes the random boot crashes.
There is still the regression that ballooning does no longer work on
s390 (see the call trace).