Messages in this thread | | | Subject | Re: [PATCH net-next V2 6/8] vhost: packed ring support | From | Maxime Coquelin <> | Date | Tue, 16 Oct 2018 15:58:22 +0200 |
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On 10/15/2018 04:22 AM, 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? > >>>> + vq->last_used_idx = s.num; >>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) >>>> + vq->last_used_wrap_counter = wrap_counter; >>>> + break; >>>> + case VHOST_GET_VRING_USED_BASE: >>> Do we need the new VHOST_GET_VRING_USED_BASE and >>> VHOST_SET_VRING_USED_BASE ops? >>> >>> We are going to merge below series in DPDK: >>> >>> http://patches.dpdk.org/patch/45874/ >>> >>> We may need to reach an agreement first. > > If we agree that 64K virtqueue won't be supported, I'm ok with either.
I'm fine to put wrap_counter at bit 15. I will post a new version of the DPDK series soon.
> Btw the code assumes used_wrap_counter is equal to avail_wrap_counter > which looks wrong?
For split ring, we used to set the last_used_idx to the same value as last_avail_idx as VHOST_USER_GET_VRING_BASE cannot be called while the ring is being processed, so their value is always the same at the time the request is handled.
I kept the same behavior for packed ring, and so the wrap counter have to be the same.
Regards, Maxime
> Thanks > >>> >>>> + s.index = idx; >>>> + s.num = vq->last_used_idx; >>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) >>>> + s.num |= vq->last_used_wrap_counter << 31; >>>> if (copy_to_user(argp, &s, sizeof s)) >>>> r = -EFAULT; >>>> break; >>> [...] >
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