From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH net-next V2 6/8] vhost: packed ring support Date: Mon, 15 Oct 2018 10:51:06 +0800 Message-ID: References: <1531711691-6769-1-git-send-email-jasowang@redhat.com> <1531711691-6769-7-git-send-email-jasowang@redhat.com> <20181012143244.GA28400@debian> <20181012131812-mutt-send-email-mst@kernel.org> <447f47fa-32dd-a408-dd81-13a9839e0748@redhat.com> <20181014224208-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Tiwei Bie , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, wexu@redhat.com, jfreimann@redhat.com, maxime.coquelin@redhat.com To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20181014224208-mutt-send-email-mst@kernel.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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. > >>>>> + 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. > Well the spec says right at the beginning: > > Packed virtqueues support up to 2 15 entries each. Ok. I get it. Then I can change vhost to match what dpdk did. Thanks > > >> 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; >>>> [...]