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Date: Mon, 15 Oct 2018 10:22:33 +0800 From: Jason Wang <jasowang@...hat.com> To: "Michael S. Tsirkin" <mst@...hat.com>, Tiwei Bie <tiwei.bie@...el.com> Cc: kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, wexu@...hat.com, jfreimann@...hat.com, maxime.coquelin@...hat.com Subject: Re: [PATCH net-next V2 6/8] vhost: packed ring support 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. Btw the code assumes used_wrap_counter is equal to avail_wrap_counter which looks wrong? 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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