Re: [Qemu-devel] [PATCH v4 11/22] vhost-user: send log shm fd along with log_base

["Michael S. Tsirkin" <mst@redhat.com>]

On Sat, Sep 19, 2015 at 12:12:02PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Send the shm for the dirty pages logging if the backend supports
> VHOST_USER_PROTOCOL_F_LOG_SHMFD.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  hw/virtio/vhost-backend.c         |  3 ++-
>  hw/virtio/vhost-user.c            | 17 ++++++++++++++---
>  hw/virtio/vhost.c                 |  5 +++--
>  include/hw/virtio/vhost-backend.h |  4 +++-
>  4 files changed, 22 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index bf2d1d4..3f2d6ea 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -66,7 +66,8 @@ static int vhost_scsi_get_abi_version(struct vhost_dev *dev, int *version)
>      return vhost_kernel_call(dev, VHOST_SCSI_GET_ABI_VERSION, version);
>  }
>  
> -static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
> +static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base,
> +                              struct vhost_log *log)
>  {
>      return vhost_kernel_call(dev, VHOST_SET_LOG_BASE, &base);
>  }
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index d3334f5..3cb5559 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -26,7 +26,9 @@
>  #define VHOST_MEMORY_MAX_NREGIONS    8
>  
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
> -#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
> +
> +#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x1ULL
> +#define VHOST_USER_PROTOCOL_F_LOG_SHMFD 0
>  
>  typedef enum VhostUserRequest {
>      VHOST_USER_NONE = 0,
> @@ -182,8 +184,11 @@ static int vhost_scsi_get_abi_version(struct vhost_dev *dev, int *version)
>      return -1;
>  }
>  
> -static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
> +static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base,
> +                              struct vhost_log *log)
>  {
> +    int fds[VHOST_MEMORY_MAX_NREGIONS];
> +    size_t fd_num = 0;
>      VhostUserMsg msg = {
>          .request = VHOST_USER_SET_LOG_BASE,
>          .flags = VHOST_USER_VERSION,
> @@ -191,7 +196,13 @@ static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
>          .size = sizeof(m.u64),
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (virtio_has_feature(dev->protocol_features,
> +                           VHOST_USER_PROTOCOL_F_LOG_SHMFD) &&
> +        log->fd != -1) {
> +        fds[fd_num++] = log->fd;
> +    }
> +
> +    vhost_user_write(dev, &msg, fds, fd_num);
>  
>      return 0;
>  }

Doesn't this one have to get a response?
Otherwise the other side might still be using the old
buffer after we've updated this one.

Probably need a protocol feature, but I guess we can reuse
VHOST_USER_PROTOCOL_F_LOG_SHMFD - IIUC logging doesn't
work without this anyway ...


> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 83ef164..0fa7b69 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -359,7 +359,7 @@ static inline void vhost_dev_log_resize(struct vhost_dev* dev, uint64_t size)
>  
>      /* inform backend of log switching, this must be done before
>         releasing the current log, to ensure no logging is lost */
> -    r = dev->vhost_ops->vhost_set_log_base(dev, log_base);
> +    r = dev->vhost_ops->vhost_set_log_base(dev, log_base, log);
>      assert(r >= 0);
>      vhost_log_put(dev, true);
>      dev->log = log;
> @@ -1167,7 +1167,8 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
>          hdev->log = vhost_log_get(hdev->log_size, share);
>          log_base = (uintptr_t)hdev->log->log;
>          r = hdev->vhost_ops->vhost_set_log_base(hdev,
> -                                                hdev->log_size ? log_base : 0);
> +                                                hdev->log_size ? log_base : 0,
> +                                                hdev->log);
>          if (r < 0) {
>              r = -errno;
>              goto fail_log;
> diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> index 42cfb87..a87f0b3 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -20,6 +20,7 @@ typedef enum VhostBackendType {
>  
>  struct vhost_dev;
>  struct vhost_memory;
> +struct vhost_log;
>  struct vhost_vring_file;
>  struct vhost_vring_state;
>  struct vhost_vring_addr;
> @@ -36,7 +37,8 @@ typedef int (*vhost_scsi_clear_endpoint_op)(struct vhost_dev *dev,
>                                              struct vhost_scsi_target *target);
>  typedef int (*vhost_scsi_get_abi_version_op)(struct vhost_dev *dev,
>                                               int *version);
> -typedef int (*vhost_set_log_base_op)(struct vhost_dev *dev, uint64_t base);
> +typedef int (*vhost_set_log_base_op)(struct vhost_dev *dev, uint64_t base,
> +                                     struct vhost_log *log);
>  typedef int (*vhost_set_mem_table_op)(struct vhost_dev *dev,
>                                        struct vhost_memory *mem);
>  typedef int (*vhost_set_vring_addr_op)(struct vhost_dev *dev,
> -- 
> 2.4.3