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

[Stefano Garzarella]

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
 };


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
>
>