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

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Date:   Wed, 13 Dec 2023 12:23:35 +0100
From:   Maxime Coquelin <maxime.coquelin@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, xuanzhuo@...ux.alibaba.com, paul@...l-moore.com,
        jmorris@...ei.org, serge@...lyn.com,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        xieyongji@...edance.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        david.marchand@...hat.com, lulu@...hat.com, casey@...aufler-ca.com
Subject: Re: [PATCH v5 2/4] vduse: Temporarily disable control queue features

Hi Jason,

On 12/13/23 05:52, Jason Wang wrote:
> On Tue, Dec 12, 2023 at 9:17 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 disable control virtqueue and features that depend on
>> it.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@...hat.com>
> 
> 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
>>
>