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SubjectRe: [PATCH v22 2/3] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ
On 01/17/2018 04:21 PM, Pankaj Gupta wrote:
>> Negotiation of the VIRTIO_BALLOON_F_FREE_PAGE_VQ feature indicates the
>> support of reporting hints of guest free pages to host via virtio-balloon.
>>
>> Host requests the guest to report free pages by sending a new cmd
>> id to the guest via the free_page_report_cmd_id configuration register.
>>
>> When the guest starts to report, the first element added to the free page
>> vq is the cmd id given by host. When the guest finishes the reporting
>> of all the free pages, VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID is added
>> to the vq to tell host that the reporting is done. Host may also requests
>> the guest to stop the reporting in advance by sending the stop cmd id to
>> the guest via the configuration register.
>>
>> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
>> Signed-off-by: Liang Li <liang.z.li@intel.com>
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> ---
>> drivers/virtio/virtio_balloon.c | 242
>> +++++++++++++++++++++++++++++++-----
>> include/uapi/linux/virtio_balloon.h | 4 +
>> 2 files changed, 214 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_balloon.c
>> b/drivers/virtio/virtio_balloon.c
>> index a1fb52c..b9561a5 100644
>> --- a/drivers/virtio/virtio_balloon.c
>> +++ b/drivers/virtio/virtio_balloon.c
>> @@ -53,7 +53,12 @@ static struct vfsmount *balloon_mnt;
>>
>> struct virtio_balloon {
>> struct virtio_device *vdev;
>> - struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
>> + struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
>> +
>> + /* Balloon's own wq for cpu-intensive work items */
>> + struct workqueue_struct *balloon_wq;
>> + /* The free page reporting work item submitted to the balloon wq */
>> + struct work_struct report_free_page_work;
>>
>> /* The balloon servicing is delegated to a freezable workqueue. */
>> struct work_struct update_balloon_stats_work;
>> @@ -63,6 +68,13 @@ struct virtio_balloon {
>> spinlock_t stop_update_lock;
>> bool stop_update;
>>
>> + /* Start to report free pages */
>> + bool report_free_page;
>> + /* Stores the cmd id given by host to start the free page reporting */
>> + uint32_t start_cmd_id;
>> + /* Stores STOP_ID as a sign to tell host that the reporting is done */
>> + uint32_t stop_cmd_id;
>> +
>> /* Waiting for host to ack the pages we released. */
>> wait_queue_head_t acked;
>>
>> @@ -281,6 +293,71 @@ static unsigned int update_balloon_stats(struct
>> virtio_balloon *vb)
>> return idx;
>> }
>>
>> +static void add_one_sg(struct virtqueue *vq, unsigned long pfn, uint32_t
>> len)
>> +{
>> + struct scatterlist sg;
>> + unsigned int unused;
>> + int err;
>> +
>> + sg_init_table(&sg, 1);
>> + sg_set_page(&sg, pfn_to_page(pfn), len, 0);
>> +
>> + /* Detach all the used buffers from the vq */
>> + while (virtqueue_get_buf(vq, &unused))
>> + ;
>> +
>> + /*
>> + * Since this is an optimization feature, losing a couple of free
>> + * pages to report isn't important. We simply resturn without adding
>> + * the page if the vq is full. We are adding one entry each time,
>> + * which essentially results in no memory allocation, so the
>> + * GFP_KERNEL flag below can be ignored.
>> + */
>> + if (vq->num_free) {
>> + err = virtqueue_add_inbuf(vq, &sg, 1, vq, GFP_KERNEL);
>> + /*
>> + * This is expected to never fail, because there is always an
>> + * entry available on the vq.
>> + */
>> + BUG_ON(err);
>> + }
>> +}
>> +
>> +static void batch_free_page_sg(struct virtqueue *vq,
>> + unsigned long pfn,
>> + uint32_t len)
>> +{
>> + add_one_sg(vq, pfn, len);
>> +
>> + /* Batch till the vq is full */
>> + if (!vq->num_free)
>> + virtqueue_kick(vq);
>> +}
>> +
>> +static void send_cmd_id(struct virtqueue *vq, void *addr)
>> +{
>> + struct scatterlist sg;
>> + unsigned int unused;
>> + int err;
>> +
>> + sg_init_one(&sg, addr, sizeof(uint32_t));
>> +
>> + /*
>> + * This handles the cornercase that the vq happens to be full when
>> + * adding a cmd id. Rarely happen in practice.
>> + */
>> + while (!vq->num_free)
>> + virtqueue_get_buf(vq, &unused);
>> +
>> + err = virtqueue_add_outbuf(vq, &sg, 1, vq, GFP_KERNEL);
>> + /*
>> + * This is expected to never fail, because there is always an
>> + * entry available on the vq.
>> + */
>> + BUG_ON(err);
>> + virtqueue_kick(vq);
>> +}
>> +
>> /*
>> * While most virtqueues communicate guest-initiated requests to the
>> hypervisor,
>> * the stats queue operates in reverse. The driver initializes the
>> virtqueue
>> @@ -316,17 +393,6 @@ static void stats_handle_request(struct virtio_balloon
>> *vb)
>> virtqueue_kick(vq);
>> }
>>
>> -static void virtballoon_changed(struct virtio_device *vdev)
>> -{
>> - struct virtio_balloon *vb = vdev->priv;
>> - unsigned long flags;
>> -
>> - spin_lock_irqsave(&vb->stop_update_lock, flags);
>> - if (!vb->stop_update)
>> - queue_work(system_freezable_wq, &vb->update_balloon_size_work);
>> - spin_unlock_irqrestore(&vb->stop_update_lock, flags);
>> -}
>> -
>> static inline s64 towards_target(struct virtio_balloon *vb)
>> {
>> s64 target;
>> @@ -343,6 +409,36 @@ static inline s64 towards_target(struct virtio_balloon
>> *vb)
>> return target - vb->num_pages;
>> }
>>
>> +static void virtballoon_changed(struct virtio_device *vdev)
>> +{
>> + struct virtio_balloon *vb = vdev->priv;
>> + unsigned long flags;
>> + __u32 cmd_id;
>> + s64 diff = towards_target(vb);
>> +
>> + if (diff) {
>> + spin_lock_irqsave(&vb->stop_update_lock, flags);
>> + if (!vb->stop_update)
>> + queue_work(system_freezable_wq,
>> + &vb->update_balloon_size_work);
>> + spin_unlock_irqrestore(&vb->stop_update_lock, flags);
>> + }
>> +
>> + virtio_cread(vb->vdev, struct virtio_balloon_config,
>> + free_page_report_cmd_id, &cmd_id);
>> + if (cmd_id == VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID) {
>> + WRITE_ONCE(vb->report_free_page, false);
>> + } else if (cmd_id != vb->start_cmd_id) {
>> + /*
>> + * Host requests to start the reporting by sending a new cmd
>> + * id.
>> + */
>> + WRITE_ONCE(vb->report_free_page, true);
>> + vb->start_cmd_id = cmd_id;
>> + queue_work(vb->balloon_wq, &vb->report_free_page_work);
>> + }
>> +}
>> +
>> static void update_balloon_size(struct virtio_balloon *vb)
>> {
>> u32 actual = vb->num_pages;
>> @@ -417,40 +513,113 @@ static void update_balloon_size_func(struct
>> work_struct *work)
>>
>> 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;
>> + vq_callback_t **callbacks;
>> + const char **names;
>> + struct scatterlist sg;
>> + int i, nvqs, err = -ENOMEM;
>> +
>> + /* Inflateq and deflateq are used unconditionally */
>> + nvqs = 2;
>> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ))
>> + nvqs++;
>> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ))
>> + nvqs++;
>> +
>> + /* Allocate space for find_vqs parameters */
>> + vqs = kcalloc(nvqs, sizeof(*vqs), GFP_KERNEL);
>> + if (!vqs)
>> + goto err_vq;
>> + callbacks = kmalloc_array(nvqs, sizeof(*callbacks), GFP_KERNEL);
>> + if (!callbacks)
>> + goto err_callback;
>> + names = kmalloc_array(nvqs, sizeof(*names), GFP_KERNEL);
>> + if (!names)
>> + goto err_names;
>> +
>> + callbacks[0] = balloon_ack;
>> + names[0] = "inflate";
>> + callbacks[1] = balloon_ack;
>> + names[1] = "deflate";
>> +
>> + i = 2;
>> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
>> + callbacks[i] = stats_request;
>> + names[i] = "stats";
>> + i++;
>> + }
>>
>> - /*
>> - * We expect two virtqueues: inflate and deflate, and
>> - * optionally stat.
>> - */
>> - nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
>> - err = virtio_find_vqs(vb->vdev, nvqs, vqs, callbacks, names, NULL);
>> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ)) {
>> + callbacks[i] = NULL;
>> + names[i] = "free_page_vq";
>> + }
>> +
>> + err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names,
>> + NULL, NULL);
>> if (err)
>> - return err;
>> + goto err_find;
>>
>> vb->inflate_vq = vqs[0];
>> vb->deflate_vq = vqs[1];
>> + i = 2;
>> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
>> - struct scatterlist sg;
>> - unsigned int num_stats;
>> - vb->stats_vq = vqs[2];
>> -
>> + vb->stats_vq = vqs[i++];
>> /*
>> * Prime this virtqueue with one buffer so the hypervisor can
>> * use it to signal us later (it can't be broken yet!).
>> */
>> - num_stats = update_balloon_stats(vb);
>> -
>> - sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
>> + sg_init_one(&sg, vb->stats, sizeof(vb->stats));
>> if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
>> - < 0)
>> - BUG();
>> + < 0) {
>> + dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
>> + __func__);
>> + goto err_find;
>> + }
>> virtqueue_kick(vb->stats_vq);
>> }
>> +
>> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ))
>> + vb->free_page_vq = vqs[i];
>> +
>> + kfree(names);
>> + kfree(callbacks);
>> + kfree(vqs);
>> return 0;
>
> We can assign err=0 and remove above duplicate code?
>

Where do you want to assign err=0? Could you show it using code?


Best,
Wei


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