Re: [PATCH v5 2/4] vduse: Temporarily disable control queue features

[Maxime Coquelin]

Hi Jason,

On 12/13/23 05:52, Jason Wang wrote:
> On Tue, Dec 12, 2023 at 9:17 PM Maxime Coquelin
> <maxime.coquelin@xxxxxxxxxx> wrote:
> > Virtio-net driver control queue implementation is not safe
> > when used with VDUSE. If the VDUSE application does not
> > reply to control queue messages, it currently ends up
> > hanging the kernel thread sending this command.
> >
> > Some work is on-going to make the control queue
> > implementation robust with VDUSE. Until it is completed,
> > let's disable control virtqueue and features that depend on
> > it.
> >
> > Signed-off-by: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>
>
> I wonder if it's better to fail instead of a mask as a start.

I think it is better to use a mask and not fail, so that we can in the
future use a recent VDUSE application with an older kernel.

Why would it be better to fail than negotiating?

Thanks,
Maxime

> Thanks
>
> > ---
> >   drivers/vdpa/vdpa_user/vduse_dev.c | 37 ++++++++++++++++++++++++++++++
> >   1 file changed, 37 insertions(+)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 0486ff672408..fe4b5c8203fd 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -28,6 +28,7 @@
> >   #include <uapi/linux/virtio_config.h>
> >   #include <uapi/linux/virtio_ids.h>
> >   #include <uapi/linux/virtio_blk.h>
> > +#include <uapi/linux/virtio_ring.h>
> >   #include <linux/mod_devicetable.h>
> >
> >   #include "iova_domain.h"
> > @@ -46,6 +47,30 @@
> >
> >   #define IRQ_UNBOUND -1
> >
> > +#define VDUSE_NET_VALID_FEATURES_MASK           \
> > +       (BIT_ULL(VIRTIO_NET_F_CSUM) |           \
> > +        BIT_ULL(VIRTIO_NET_F_GUEST_CSUM) |     \
> > +        BIT_ULL(VIRTIO_NET_F_MTU) |            \
> > +        BIT_ULL(VIRTIO_NET_F_MAC) |            \
> > +        BIT_ULL(VIRTIO_NET_F_GUEST_TSO4) |     \
> > +        BIT_ULL(VIRTIO_NET_F_GUEST_TSO6) |     \
> > +        BIT_ULL(VIRTIO_NET_F_GUEST_ECN) |      \
> > +        BIT_ULL(VIRTIO_NET_F_GUEST_UFO) |      \
> > +        BIT_ULL(VIRTIO_NET_F_HOST_TSO4) |      \
> > +        BIT_ULL(VIRTIO_NET_F_HOST_TSO6) |      \
> > +        BIT_ULL(VIRTIO_NET_F_HOST_ECN) |       \
> > +        BIT_ULL(VIRTIO_NET_F_HOST_UFO) |       \
> > +        BIT_ULL(VIRTIO_NET_F_MRG_RXBUF) |      \
> > +        BIT_ULL(VIRTIO_NET_F_STATUS) |         \
> > +        BIT_ULL(VIRTIO_NET_F_HOST_USO) |       \
> > +        BIT_ULL(VIRTIO_F_ANY_LAYOUT) |         \
> > +        BIT_ULL(VIRTIO_RING_F_INDIRECT_DESC) | \
> > +        BIT_ULL(VIRTIO_RING_F_EVENT_IDX) |          \
> > +        BIT_ULL(VIRTIO_F_VERSION_1) |          \
> > +        BIT_ULL(VIRTIO_F_ACCESS_PLATFORM) |     \
> > +        BIT_ULL(VIRTIO_F_RING_PACKED) |        \
> > +        BIT_ULL(VIRTIO_F_IN_ORDER))
> > +
> >   struct vduse_virtqueue {
> >          u16 index;
> >          u16 num_max;
> > @@ -1782,6 +1807,16 @@ static struct attribute *vduse_dev_attrs[] = {
> >
> >   ATTRIBUTE_GROUPS(vduse_dev);
> >
> > +static void vduse_dev_features_filter(struct vduse_dev_config *config)
> > +{
> > +       /*
> > +        * Temporarily filter out virtio-net's control virtqueue and features
> > +        * that depend on it while CVQ is being made more robust for VDUSE.
> > +        */
> > +       if (config->device_id == VIRTIO_ID_NET)
> > +               config->features &= VDUSE_NET_VALID_FEATURES_MASK;
> > +}
> > +
> >   static int vduse_create_dev(struct vduse_dev_config *config,
> >                              void *config_buf, u64 api_version)
> >   {
> > @@ -1797,6 +1832,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
> >          if (!dev)
> >                  goto err;
> >
> > +       vduse_dev_features_filter(config);
> > +
> >          dev->api_version = api_version;
> >          dev->device_features = config->features;
> >          dev->device_id = config->device_id;
> > --
> > 2.43.0