Messages in this thread | | | Subject | Re: [PATCH] vhost: introduce mdev based hardware backend | From | Jason Wang <> | Date | Sun, 29 Sep 2019 15:39:05 +0800 |
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On 2019/9/27 下午9:23, Michael S. Tsirkin wrote: > On Fri, Sep 27, 2019 at 09:17:56PM +0800, Jason Wang wrote: >> On 2019/9/27 下午8:46, Michael S. Tsirkin wrote: >>> On Fri, Sep 27, 2019 at 08:17:47PM +0800, Jason Wang wrote: >>>> On 2019/9/27 下午5:41, Michael S. Tsirkin wrote: >>>>> On Fri, Sep 27, 2019 at 11:27:12AM +0800, Jason Wang wrote: >>>>>> On 2019/9/26 下午9:14, Tiwei Bie wrote: >>>>>>> On Thu, Sep 26, 2019 at 04:35:18AM -0400, Michael S. Tsirkin wrote: >>>>>>>> On Thu, Sep 26, 2019 at 12:54:27PM +0800, Tiwei Bie wrote: >>>>>>> [...] >>>>>>>>> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h >>>>>>>>> index 40d028eed645..5afbc2f08fa3 100644 >>>>>>>>> --- a/include/uapi/linux/vhost.h >>>>>>>>> +++ b/include/uapi/linux/vhost.h >>>>>>>>> @@ -116,4 +116,12 @@ >>>>>>>>> #define VHOST_VSOCK_SET_GUEST_CID _IOW(VHOST_VIRTIO, 0x60, __u64) >>>>>>>>> #define VHOST_VSOCK_SET_RUNNING _IOW(VHOST_VIRTIO, 0x61, int) >>>>>>>>> +/* VHOST_MDEV specific defines */ >>>>>>>>> + >>>>>>>>> +#define VHOST_MDEV_SET_STATE _IOW(VHOST_VIRTIO, 0x70, __u64) >>>>>>>>> + >>>>>>>>> +#define VHOST_MDEV_S_STOPPED 0 >>>>>>>>> +#define VHOST_MDEV_S_RUNNING 1 >>>>>>>>> +#define VHOST_MDEV_S_MAX 2 >>>>>>>>> + >>>>>>>>> #endif >>>>>>>> So assuming we have an underlying device that behaves like virtio: >>>>>>> I think they are really good questions/suggestions. Thanks! >>>>>>> >>>>>>>> 1. Should we use SET_STATUS maybe? >>>>>>> I like this idea. I will give it a try. >>>>>>> >>>>>>>> 2. Do we want a reset ioctl? >>>>>>> I think it is helpful. If we use SET_STATUS, maybe we >>>>>>> can use it to support the reset. >>>>>>> >>>>>>>> 3. Do we want ability to enable rings individually? >>>>>>> I will make it possible at least in the vhost layer. >>>>>> Note the API support e.g set_vq_ready(). >>>>> virtio spec calls this "enabled" so let's stick to that. >>>> Ok. >>>> >>>> >>>>>>>> 4. Does device need to limit max ring size? >>>>>>>> 5. Does device need to limit max number of queues? >>>>>>> I think so. It's helpful to have ioctls to report the max >>>>>>> ring size and max number of queues. >>>>>> An issue is the max number of queues is done through a device specific way, >>>>>> usually device configuration space. This is supported by the transport API, >>>>>> but how to expose it to userspace may need more thought. >>>>>> >>>>>> Thanks >>>>> an ioctl for device config? But for v1 I'd be quite happy to just have >>>>> a minimal working device with 2 queues. >>>> I'm fully agree, and it will work as long as VIRTIO_NET_F_MQ and >>>> VIRTIO_NET_F_CTRL_VQ is not advertised by the mdev device. >>>> >>>> Thanks >>> Hmm this means we need to validate the features bits, >>> not just pass them through to the hardware. >>> Problem is, how do we add more feature bits later, >>> without testing all hardware? >>> I guess this means the device specific driver must do it. >>> >> That looks not good, maybe a virtio device id based features blacklist in >> vhost-mdev. Then MQ and CTRL_VQ could be filtered out by vhost-mdev. >> >> Thanks > Two implementations of e.g. virtio net can have different > features whitelisted.
I meant for kernel driver, we won't blacklist any feature, but for vhost-mdev, we need to do that.
> So I think there's no way but let > the driver do it. We should probably provide a standard place > in the ops for driver to supply the whitelist, to make sure > drivers don't forget.
For 'driver' do you mean userspace driver of the mdev device?
Thanks
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