Re: [PATCH] vhost: Not return fail while the device does not support send_iotlb_msg

[Cindy Lu]

On Thu, 1 Dec 2022 at 16:49, Jason Wang <jasowang@redhat.com> wrote:
>
> On Wed, Nov 30, 2022 at 4:11 PM Cindy Lu <lulu@redhat.com> wrote:
> >
> > Some device does not support vhost_send_device_iotlb_msg()
> > such as vDPA device, which is as expected. So we should not
> > return fail here.
>
> Please explain in which case you may hit the -ENODEV and what's the
> side effect of this.
>
> Thanks
>
this issue was found during the test of virtio-iommu
the step is
1. while load the VM with qemu
  -device virtio-iommu-pci \
  -device 
virtio-net-pci,netdev=vhost-vdpa0,disable-legacy=on,disable-modern=off,iommu_platform=on\
  -netdev type=vhost-vdpa,vhostdev=/dev/vhost-vdpa-0,id=vhost-vdpa0\
2.  the guest vm's CMDLINE //proc/cmdline don't have  iommu=pt
there will be a lot error message during loading VM/runing traffic
ysteqemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
mqemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
dqemu-system-x86_64: Fail to invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
-resolved.…e - Network Name Resolution...qemu-system-x86_64: Fail to
invalidate device iotlb
qemu-system-x86_64: Fail to invalidate device iotlb
.....
and the vdpa port in guest VM doesn't working  well

With this fix the guest VM load without error message and the vdpa
port working correctly at the
same setting
[root@ubuntunew ~]# ping 111.1.1.2
PING 111.1.1.2 (111.1.1.2) 56(84) bytes of data.
64 bytes from 111.1.1.2: icmp_seq=1 ttl=64 time=25.0 ms
64 bytes from 111.1.1.2: icmp_seq=2 ttl=64 time=22.0 ms
64 bytes from 111.1.1.2: icmp_seq=3 ttl=64 time=24.3 ms

Thansk
Cindy

> >
> > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > ---
> >  hw/virtio/vhost-backend.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> > index 8e581575c9..9321ed9031 100644
> > --- a/hw/virtio/vhost-backend.c
> > +++ b/hw/virtio/vhost-backend.c
> > @@ -360,7 +360,7 @@ int vhost_backend_update_device_iotlb(struct vhost_dev 
> > *dev,
> >      if (dev->vhost_ops && dev->vhost_ops->vhost_send_device_iotlb_msg)
> >          return dev->vhost_ops->vhost_send_device_iotlb_msg(dev, &imsg);
> >
> > -    return -ENODEV;
> > +    return 0;
> >  }
> >
> >  int vhost_backend_invalidate_device_iotlb(struct vhost_dev *dev,
> > @@ -375,7 +375,7 @@ int vhost_backend_invalidate_device_iotlb(struct 
> > vhost_dev *dev,
> >      if (dev->vhost_ops && dev->vhost_ops->vhost_send_device_iotlb_msg)
> >          return dev->vhost_ops->vhost_send_device_iotlb_msg(dev, &imsg);
> >
> > -    return -ENODEV;
> > +    return 0;
> >  }
> >
> >  int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
> > --
> > 2.34.3
> >
>