Messages in this thread | | | Subject | Re: [PATCH net-next V2 6/8] vhost: packed ring support | From | Jason Wang <> | Date | Thu, 18 Oct 2018 10:44:36 +0800 |
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On 2018/10/15 下午6:25, Michael S. Tsirkin wrote: > On Mon, Oct 15, 2018 at 10:51:06AM +0800, Jason Wang wrote: >> On 2018年10月15日 10:43, Michael S. Tsirkin wrote: >>> On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote: >>>> On 2018年10月13日 01:23, Michael S. Tsirkin wrote: >>>>> On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote: >>>>>> On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote: >>>>>> [...] >>>>>>> @@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg >>>>>>> vq->last_avail_idx = s.num; >>>>>>> /* Forget the cached index value. */ >>>>>>> vq->avail_idx = vq->last_avail_idx; >>>>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) { >>>>>>> + vq->last_avail_wrap_counter = wrap_counter; >>>>>>> + vq->avail_wrap_counter = vq->last_avail_wrap_counter; >>>>>>> + } >>>>>>> break; >>>>>>> case VHOST_GET_VRING_BASE: >>>>>>> s.index = idx; >>>>>>> s.num = vq->last_avail_idx; >>>>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) >>>>>>> + s.num |= vq->last_avail_wrap_counter << 31; >>>>>>> + if (copy_to_user(argp, &s, sizeof(s))) >>>>>>> + r = -EFAULT; >>>>>>> + break; >>>>>>> + case VHOST_SET_VRING_USED_BASE: >>>>>>> + /* Moving base with an active backend? >>>>>>> + * You don't want to do that. >>>>>>> + */ >>>>>>> + if (vq->private_data) { >>>>>>> + r = -EBUSY; >>>>>>> + break; >>>>>>> + } >>>>>>> + if (copy_from_user(&s, argp, sizeof(s))) { >>>>>>> + r = -EFAULT; >>>>>>> + break; >>>>>>> + } >>>>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) { >>>>>>> + wrap_counter = s.num >> 31; >>>>>>> + s.num &= ~(1 << 31); >>>>>>> + } >>>>>>> + if (s.num > 0xffff) { >>>>>>> + r = -EINVAL; >>>>>>> + break; >>>>>>> + } >>>>>> Do we want to put wrap_counter at bit 15? >>>>> I think I second that - seems to be consistent with >>>>> e.g. event suppression structure and the proposed >>>>> extension to driver notifications. >>>> Ok, I assumes packed virtqueue support 64K but looks not. I can change it to >>>> bit 15 and GET_VRING_BASE need to be changed as well. >>>> >>>>>> If put wrap_counter at bit 31, the check (s.num > 0xffff) >>>>>> won't be able to catch the illegal index 0x8000~0xffff for >>>>>> packed ring. >>>>>> >>>> Do we need to clarify this in the spec? >>> Isn't this all internal vhost stuff? >> I meant the illegal index 0x8000-0xffff. > It does say packed virtqueues support up to 2 15 entries each. > > But yes we can add a requirement that devices do not expose > larger rings. Split does not support 2**16 either, right? > With 2**16 enties avail index becomes 0 and ring looks empty. >
Yes, so it's better to clarify this in the spec.
Thanks
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