Re: [PATCH v1 09/10] vhost-vdpa: introduce vhost-vdpa backend

[Cindy Lu]

On Thu, Jun 25, 2020 at 8:37 PM Laurent Vivier <lvivier@redhat.com> wrote:
>
> On 22/06/2020 17:37, Cindy Lu wrote:
> > Currently we have 2 types of vhost backends in QEMU: vhost kernel and
> > vhost-user. The above patch provides a generic device for vDPA purpose,
> > this vDPA device exposes to user space a non-vendor-specific configuration
> > interface for setting up a vhost HW accelerator, this patch set introduces
> > a third vhost backend called vhost-vdpa based on the vDPA interface.
> >
> > Vhost-vdpa usage:
> >
> > qemu-system-x86_64 -cpu host -enable-kvm \
> >     ......
> >     -netdev type=vhost-vdpa,vhostdev=/dev/vhost-vdpa-id,id=vhost-vdpa0 \
> >     -device virtio-net-pci,netdev=vhost-vdpa0,page-per-vq=on \
> >
> > Signed-off-by: Lingshan zhu <lingshan.zhu@intel.com>
> > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > ---
> >  configure                         |  21 ++
> >  hw/net/vhost_net.c                |  19 +-
> >  hw/net/virtio-net.c               |  19 +-
> >  hw/virtio/Makefile.objs           |   1 +
> >  hw/virtio/vhost-backend.c         |  22 +-
> >  hw/virtio/vhost-vdpa.c            | 406 ++++++++++++++++++++++++++++++
> >  hw/virtio/vhost.c                 |  42 +++-
> >  include/hw/virtio/vhost-backend.h |   6 +-
> >  include/hw/virtio/vhost-vdpa.h    |  26 ++
> >  include/hw/virtio/vhost.h         |   6 +
> >  qemu-options.hx                   |  12 +
> >  11 files changed, 555 insertions(+), 25 deletions(-)
> >  create mode 100644 hw/virtio/vhost-vdpa.c
> >  create mode 100644 include/hw/virtio/vhost-vdpa.h
> >
> ...
> > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> > index 660e9e8588..84e5b1a833 100644
> > --- a/hw/virtio/vhost-backend.c
> > +++ b/hw/virtio/vhost-backend.c
> > @@ -14,7 +14,7 @@
> >  #include "qemu/error-report.h"
> >  #include "qemu/main-loop.h"
> >  #include "standard-headers/linux/vhost_types.h"
> > -
> > +#include "hw/virtio/vhost-vdpa.h"
> >  #ifdef CONFIG_VHOST_KERNEL
> >  #include <linux/vhost.h>
> >  #include <sys/ioctl.h>
> > @@ -22,10 +22,19 @@
> >  static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int 
> > request,
> >                               void *arg)
> >  {
> > -    int fd = (uintptr_t) dev->opaque;
> > -
> > -    assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
> > +    int fd = -1;
>
> You don't need to initialize fd before the switch() because all cases
> will set a value to it or assert.
>
> > +    switch (dev->vhost_ops->backend_type) {
> > +    case VHOST_BACKEND_TYPE_KERNEL:
> > +        fd  = (uintptr_t)dev->opaque;
> > +        break;
> > +    case VHOST_BACKEND_TYPE_VDPA:
> > +        fd = ((struct vhost_vdpa *)dev->opaque)->device_fd;
> > +        break;
> > +    default:
> > +        g_assert_not_reached();
> > +    }
> >
> > +    assert(fd != -1);
>
> Perhaps this assert is not needed:
> Unitialized value will be catched by "default:", and there was no such
> kind of check on "(uintptr_t)dev->opaque" before.
>
sure, thanks will fix this
> Thanks,
> Laurent
>