Re: [Qemu-devel] [PATCH v4 12/22] vhost: only use shared log if in use by backend

["Marc-André Lureau" <mlureau@redhat.com>]

Hi

----- Original Message -----
> On Sat, Sep 19, 2015 at 12:12:03PM +0200, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > 
> > Do not allocate a shared log if the backend doesn't support it.
> > 
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> If not there, we probably want to block live migration, correct?

That make sense to me, I'll add that.

> > ---
> >  hw/virtio/vhost-user.c            |  9 +++++++++
> >  hw/virtio/vhost.c                 | 15 ++++++++++-----
> >  include/hw/virtio/vhost-backend.h |  4 ++++
> >  3 files changed, 23 insertions(+), 5 deletions(-)
> > 
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index 3cb5559..d12cd66 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -508,10 +508,19 @@ static int vhost_user_cleanup(struct vhost_dev *dev)
> >      return 0;
> >  }
> >  
> > +static bool vhost_user_want_shm_log(struct vhost_dev *dev)
> > +{
> > +    assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
> > +
> > +    return virtio_has_feature(dev->protocol_features,
> > +                              VHOST_USER_PROTOCOL_F_LOG_SHMFD);
> > +}
> > +
> >  const VhostOps user_ops = {
> >          .backend_type = VHOST_BACKEND_TYPE_USER,
> >          .vhost_backend_init = vhost_user_init,
> >          .vhost_backend_cleanup = vhost_user_cleanup,
> > +        .vhost_backend_want_shm_log = vhost_user_want_shm_log,
> >  
> >          .vhost_net_set_backend = vhost_net_set_backend,
> >          .vhost_scsi_set_endpoint = vhost_scsi_set_endpoint,
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index 0fa7b69..d5070fb 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -350,10 +350,15 @@ static void vhost_log_put(struct vhost_dev *dev, bool
> > sync)
> >      }
> >  }
> >  
> > -static inline void vhost_dev_log_resize(struct vhost_dev* dev, uint64_t
> > size)
> > +static bool vhost_dev_log_is_shared(struct vhost_dev *dev)
> >  {
> > -    bool share = dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER;
> > -    struct vhost_log *log = vhost_log_get(size, share);
> > +    return dev->vhost_ops->vhost_backend_want_shm_log &&
> > +           dev->vhost_ops->vhost_backend_want_shm_log(dev);
> > +}
> > +
> > +static inline void vhost_dev_log_resize(struct vhost_dev *dev, uint64_t
> > size)
> > +{
> > +    struct vhost_log *log = vhost_log_get(size,
> > vhost_dev_log_is_shared(dev));
> >      uint64_t log_base = (uintptr_t)log->log;
> >      int r;
> >  
> > @@ -1161,10 +1166,10 @@ int vhost_dev_start(struct vhost_dev *hdev,
> > VirtIODevice *vdev)
> >  
> >      if (hdev->log_enabled) {
> >          uint64_t log_base;
> > -        bool share = hdev->vhost_ops->backend_type ==
> > VHOST_BACKEND_TYPE_USER;
> >  
> >          hdev->log_size = vhost_get_log_size(hdev);
> > -        hdev->log = vhost_log_get(hdev->log_size, share);
> > +        hdev->log = vhost_log_get(hdev->log_size,
> > +                                  vhost_dev_log_is_shared(hdev));
> >          log_base = (uintptr_t)hdev->log->log;
> >          r = hdev->vhost_ops->vhost_set_log_base(hdev,
> >                                                  hdev->log_size ? log_base
> >                                                  : 0,
> > diff --git a/include/hw/virtio/vhost-backend.h
> > b/include/hw/virtio/vhost-backend.h
> > index a87f0b3..44bf200 100644
> > --- a/include/hw/virtio/vhost-backend.h
> > +++ b/include/hw/virtio/vhost-backend.h
> > @@ -11,6 +11,8 @@
> >  #ifndef VHOST_BACKEND_H_
> >  #define VHOST_BACKEND_H_
> >  
> > +#include <stdbool.h>
> > +
> >  typedef enum VhostBackendType {
> >      VHOST_BACKEND_TYPE_NONE = 0,
> >      VHOST_BACKEND_TYPE_KERNEL = 1,
> > @@ -28,6 +30,7 @@ struct vhost_scsi_target;
> >  
> >  typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque);
> >  typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev);
> > +typedef bool (*vhost_backend_want_shm_log)(struct vhost_dev *dev);
> >  
> >  typedef int (*vhost_net_set_backend_op)(struct vhost_dev *dev,
> >                                          struct vhost_vring_file *file);
> > @@ -67,6 +70,7 @@ typedef struct VhostOps {
> >  
> >      vhost_backend_init vhost_backend_init;
> >      vhost_backend_cleanup vhost_backend_cleanup;
> > +    vhost_backend_want_shm_log vhost_backend_want_shm_log;
> >  
> >      vhost_net_set_backend_op vhost_net_set_backend;
> >      vhost_scsi_set_endpoint_op vhost_scsi_set_endpoint;
> > --
> > 2.4.3
>