Re: [PULL v4 30/83] virtio: core: vq reset feature negotation support

[Michael S. Tsirkin]

On Fri, Nov 18, 2022 at 03:32:56PM +0100, Stefano Garzarella wrote:
> Hi,
> starting from this commit 69e1c14aa2 ("virtio: core: vq reset feature 
> negotation support"), vhost-user-vsock and vhost-vsock fails while 
> setting the device features, because VIRTIO_F_RING_RESET is not masked.
> 
> I'm not sure vsock is the only one affected.
> 
> We could fix in two ways:
> 
> 1) Masking VIRTIO_F_RING_RESET when we call vhost_get_features:
> 
> diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
> index 29b9ab4f72..e671cc695f 100644
> --- a/hw/virtio/vhost-vsock-common.c
> +++ b/hw/virtio/vhost-vsock-common.c
> @@ -21,6 +21,7 @@
>  
>  const int feature_bits[] = {
>      VIRTIO_VSOCK_F_SEQPACKET,
> +    VIRTIO_F_RING_RESET,
>      VHOST_INVALID_FEATURE_BIT
>  };
> 

Let's do this, we need to be conservative.


> 2) Or using directly the features of the device. That way we also handle 
> other features that we may have already had to mask but never did.
> 
> diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
> index 29b9ab4f72..41a665082c 100644
> --- a/hw/virtio/vhost-vsock-common.c
> +++ b/hw/virtio/vhost-vsock-common.c
> @@ -33,7 +33,7 @@ uint64_t vhost_vsock_common_get_features(VirtIODevice 
> *vdev, uint64_t features,
>          virtio_add_feature(&features, VIRTIO_VSOCK_F_SEQPACKET);
>      }
> 
> -    features = vhost_get_features(&vvc->vhost_dev, feature_bits, features);
> +    features &= vvc->vhost_dev.features;
> 
>      if (vvc->seqpacket == ON_OFF_AUTO_ON &&
>          !virtio_has_feature(features, VIRTIO_VSOCK_F_SEQPACKET)) {
> 
> 
> I may be missing the real reason for calling vhost_get_features(), 
> though.
> 
> @Michael what do you recommend we do?
> 
> Thanks,
> Stefano
> 
> On Tue, Nov 8, 2022 at 12:06 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > From: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> >
> > A a new command line parameter "queue_reset" is added.
> >
> > Meanwhile, the vq reset feature is disabled for pre-7.2 machines.
> >
> > Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > Acked-by: Jason Wang <jasowang@redhat.com>
> > Message-Id: <20221017092558.111082-5-xuanzhuo@linux.alibaba.com>
> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  include/hw/virtio/virtio.h | 4 +++-
> >  hw/core/machine.c          | 4 +++-
> >  2 files changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index b00b3fcf31..1423dba379 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -313,7 +313,9 @@ typedef struct VirtIORNGConf VirtIORNGConf;
> >      DEFINE_PROP_BIT64("iommu_platform", _state, _field, \
> >                        VIRTIO_F_IOMMU_PLATFORM, false), \
> >      DEFINE_PROP_BIT64("packed", _state, _field, \
> > -                      VIRTIO_F_RING_PACKED, false)
> > +                      VIRTIO_F_RING_PACKED, false), \
> > +    DEFINE_PROP_BIT64("queue_reset", _state, _field, \
> > +                      VIRTIO_F_RING_RESET, true)
> >
> >  hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n);
> >  bool virtio_queue_enabled_legacy(VirtIODevice *vdev, int n);
> > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > index aa520e74a8..907fa78ff0 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -40,7 +40,9 @@
> >  #include "hw/virtio/virtio-pci.h"
> >  #include "qom/object_interfaces.h"
> >
> > -GlobalProperty hw_compat_7_1[] = {};
> > +GlobalProperty hw_compat_7_1[] = {
> > +    { "virtio-device", "queue_reset", "false" },
> > +};
> >  const size_t hw_compat_7_1_len = G_N_ELEMENTS(hw_compat_7_1);
> >
> >  GlobalProperty hw_compat_7_0[] = {
> > --
> > MST
> >
> >