linux-kernel - Re: [PATCH v6 2/3] vduse: Temporarily fail if control queue features requested

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Date: Fri, 5 Jan 2024 10:59:03 +0100
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Maxime Coquelin <maxime.coquelin@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>, mst@...hat.com, xuanzhuo@...ux.alibaba.com, 
	xieyongji@...edance.com, virtualization@...ts.linux-foundation.org, 
	linux-kernel@...r.kernel.org, david.marchand@...hat.com, lulu@...hat.com
Subject: Re: [PATCH v6 2/3] vduse: Temporarily fail if control queue features requested

On Fri, Jan 5, 2024 at 9:12 AM Maxime Coquelin
<maxime.coquelin@...hat.com> wrote:
>
>
>
> On 1/5/24 03:45, Jason Wang wrote:
> > On Thu, Jan 4, 2024 at 11:38 PM Maxime Coquelin
> > <maxime.coquelin@...hat.com> 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 fail features check if any control-queue related
> >> feature is requested.
> >>
> >> Signed-off-by: Maxime Coquelin <maxime.coquelin@...hat.com>
> >> ---
> >>   drivers/vdpa/vdpa_user/vduse_dev.c | 13 +++++++++++++
> >>   1 file changed, 13 insertions(+)
> >>
> >> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> >> index 0486ff672408..94f54ea2eb06 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 +47,15 @@
> >>
> >>   #define IRQ_UNBOUND -1
> >>
> >> +#define VDUSE_NET_INVALID_FEATURES_MASK         \
> >> +       (BIT_ULL(VIRTIO_NET_F_CTRL_VQ) |        \
> >> +        BIT_ULL(VIRTIO_NET_F_CTRL_RX)   |      \
> >> +        BIT_ULL(VIRTIO_NET_F_CTRL_VLAN) |      \
> >> +        BIT_ULL(VIRTIO_NET_F_GUEST_ANNOUNCE) | \
> >> +        BIT_ULL(VIRTIO_NET_F_MQ) |             \
> >> +        BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR) |  \
> >> +        BIT_ULL(VIRTIO_NET_F_RSS))
> >
> > We need to make this as well:
> >
> > VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
>
> I missed it, and see others have been added in the Virtio spec
> repository (BTW, I see this specific one is missing in the dependency
> list [0], I will submit a patch).
>
> I wonder if it is not just simpler to just check for
> VIRTIO_NET_F_CTRL_VQ is requested. As we fail instead of masking out,
> the VDUSE driver won't be the one violating the spec so it should be
> good?
>
> It will avoid having to update the mask if new features depending on it
> are added (or forgetting to update it).
>
> WDYT?
>

I think it is safer to work with a whitelist, instead of a blacklist.
As any new feature might require code changes in QEMU. Is that
possible?

> Thanks,
> Maxime
>
> [0]:
> https://github.com/oasis-tcs/virtio-spec/blob/5fc35a7efb903fc352da81a6d2be5c01810b68d3/device-types/net/description.tex#L129
> > Other than this,
> >
> > Acked-by: Jason Wang <jasowang@...hat.com>
> >
> > Thanks
> >
> >> +
> >>   struct vduse_virtqueue {
> >>          u16 index;
> >>          u16 num_max;
> >> @@ -1680,6 +1690,9 @@ static bool features_is_valid(struct vduse_dev_config *config)
> >>          if ((config->device_id == VIRTIO_ID_BLOCK) &&
> >>                          (config->features & (1ULL << VIRTIO_BLK_F_CONFIG_WCE)))
> >>                  return false;
> >> +       else if ((config->device_id == VIRTIO_ID_NET) &&
> >> +                       (config->features & VDUSE_NET_INVALID_FEATURES_MASK))
> >> +               return false;
> >>
> >>          return true;
> >>   }
> >> --
> >> 2.43.0
> >>
> >
>
>