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Subject: Re: [PATCH v12 8/8] virtio-balloon: VIRTIO_BALLOON_F_CMD_VQ
On 07/13/2017 08:22 AM, Michael S. Tsirkin wrote:
On Wed, Jul 12, 2017 at 08:40:21PM +0800, Wei Wang wrote:Add a new vq, cmdq, to handle requests between the device and driver. This patch implements two commands sent from the device and handled in the driver. 1) VIRTIO_BALLOON_CMDQ_REPORT_STATS: this command is used to report the guest memory statistics to the host. The stats_vq mechanism is not used when the cmdq mechanism is enabled. 2) VIRTIO_BALLOON_CMDQ_REPORT_UNUSED_PAGES: this command is used to report the guest unused pages to the host. Since now we have a vq to handle multiple commands, we need to keep only one vq operation at a time. Here, we change the existing START_USE() and END_USE() to lock on each vq operation. Signed-off-by: Wei Wang <wei.w.wang@intel.com> Signed-off-by: Liang Li <liang.z.li@intel.com> --- drivers/virtio/virtio_balloon.c | 245 ++++++++++++++++++++++++++++++++++-- drivers/virtio/virtio_ring.c | 25 +++- include/linux/virtio.h | 2 + include/uapi/linux/virtio_balloon.h | 10 ++ 4 files changed, 265 insertions(+), 17 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index aa4e7ec..ae91fbf 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -54,11 +54,12 @@ 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, *cmd_vq;/* The balloon servicing is delegated to a freezable workqueue. */struct work_struct update_balloon_stats_work; struct work_struct update_balloon_size_work; + struct work_struct cmdq_handle_work;/* Prevent updating balloon when it is being canceled. */spinlock_t stop_update_lock; @@ -90,6 +91,12 @@ struct virtio_balloon { /* Memory statistics */ struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];+ /* Cmdq msg buffer for memory statistics */+ struct virtio_balloon_cmdq_hdr cmdq_stats_hdr; + + /* Cmdq msg buffer for reporting ununsed pages */ + struct virtio_balloon_cmdq_hdr cmdq_unused_page_hdr; + /* To register callback in oom notifier call chain */ struct notifier_block nb; }; @@ -485,25 +492,214 @@ static void update_balloon_size_func(struct work_struct *work) queue_work(system_freezable_wq, work); }+static unsigned int cmdq_hdr_add(struct virtqueue *vq,+ struct virtio_balloon_cmdq_hdr *hdr, + bool in) +{ + unsigned int id = VIRTQUEUE_DESC_ID_INIT; + uint64_t hdr_pa = (uint64_t)virt_to_phys((void *)hdr); + + virtqueue_add_chain_desc(vq, hdr_pa, sizeof(*hdr), &id, &id, in); + + /* Deliver the hdr for the host to send commands. */ + if (in) { + hdr->flags = 0; + virtqueue_add_chain(vq, id, 0, NULL, hdr, NULL); + virtqueue_kick(vq); + } + + return id; +} + +static void cmdq_add_chain_desc(struct virtio_balloon *vb, + struct virtio_balloon_cmdq_hdr *hdr, + uint64_t addr, + uint32_t len, + unsigned int *head_id, + unsigned int *prev_id) +{ +retry: + if (*head_id == VIRTQUEUE_DESC_ID_INIT) { + *head_id = cmdq_hdr_add(vb->cmd_vq, hdr, 0); + *prev_id = *head_id; + } + + virtqueue_add_chain_desc(vb->cmd_vq, addr, len, head_id, prev_id, 0); + if (*head_id == *prev_id) {That's an ugly way to detect ring full.
It's actually not detecting ring full. I will call it tail_id, instead of prev_id.
So, *head_id == *tail_id is the case that the first desc was just added by virtqueue_add_chain_desc(). Best, Wei
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