From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [RFC PATCH 01/12] virtio/s390: use vring_create_virtqueue Date: Mon, 8 Apr 2019 13:01:28 +0200 Message-ID: <20190408130128.7859febe.cohuck@redhat.com> References: <20190404231622.52531-1-pasic@linux.ibm.com> <20190404231622.52531-2-pasic@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190404231622.52531-2-pasic@linux.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Halil Pasic Cc: Vasily Gorbik , linux-s390@vger.kernel.org, Eric Farman , Claudio Imbrenda , kvm@vger.kernel.org, Sebastian Ott , "Michael S . Tsirkin" , Farhan Ali , virtualization@lists.linux-foundation.org, Martin Schwidefsky , Viktor Mihajlovski , Janosch Frank List-Id: virtualization@lists.linuxfoundation.org On Fri, 5 Apr 2019 01:16:11 +0200 Halil Pasic wrote: > The commit 2a2d1382fe9d ("virtio: Add improved queue allocation API") > establishes a new way of allocating virtqueues (as a part of the effort > that taught DMA to virtio rings). > > In the future we will want virtio-ccw to use the DMA API as well. > > Let us switch from the legacy method of allocating virtqueues to > vring_create_virtqueue() as the first step into that direction. > > Signed-off-by: Halil Pasic > --- > drivers/s390/virtio/virtio_ccw.c | 27 ++++++++------------------- > 1 file changed, 8 insertions(+), 19 deletions(-) > > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c > index 74c328321889..edf4afe2d688 100644 > --- a/drivers/s390/virtio/virtio_ccw.c > +++ b/drivers/s390/virtio/virtio_ccw.c > @@ -516,17 +512,10 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev, > err = info->num; > goto out_err; > } > - size = PAGE_ALIGN(vring_size(info->num, KVM_VIRTIO_CCW_RING_ALIGN)); > - info->queue = alloc_pages_exact(size, GFP_KERNEL | __GFP_ZERO); > - if (info->queue == NULL) { > - dev_warn(&vcdev->cdev->dev, "no queue\n"); > - err = -ENOMEM; > - goto out_err; > - } > + vq = vring_create_virtqueue(i, info->num, KVM_VIRTIO_CCW_RING_ALIGN, > + vdev, true, true, ctx, This second true means 'may_reduce_num'. Looking at the vring code, it seems that this parameter is never checked; the code will try to allocate a smaller queue if it can't get the requested size in any case... this will probably be a problem for legacy virtio-pci, which explicitly sets may_reduce_num to false. (I can try to come up with a patch to fix that.) > + virtio_ccw_kvm_notify, callback, name); > > - vq = vring_new_virtqueue(i, info->num, KVM_VIRTIO_CCW_RING_ALIGN, vdev, > - true, ctx, info->queue, virtio_ccw_kvm_notify, > - callback, name); > if (!vq) { > /* For now, we fail if we can't get the requested size. */ > dev_warn(&vcdev->cdev->dev, "no vq\n"); > @@ -534,15 +523,17 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev, > goto out_err; > } > > + Extra blank line :) > /* Register it with the host. */ > + queue = virtqueue_get_desc_addr(vq); > if (vcdev->revision == 0) { > - info->info_block->l.queue = (__u64)info->queue; > + info->info_block->l.queue = queue; > info->info_block->l.align = KVM_VIRTIO_CCW_RING_ALIGN; > info->info_block->l.index = i; > info->info_block->l.num = info->num; You always fill in the size requested by the host, but the actual size may be smaller (see above). I don't think that is allowed for revision 0 (which implies !virtio-1). You probably need to call vring_create_virtqueue with may_reduce_num=false for revision 0 (and wait for the generic vring code to be fixed...) > ccw->count = sizeof(info->info_block->l); > } else { > - info->info_block->s.desc = (__u64)info->queue; > + info->info_block->s.desc = queue; > info->info_block->s.index = i; > info->info_block->s.num = info->num; Here, you need to obtain the actual number via virtqueue_get_vring_size(). > info->info_block->s.avail = (__u64)virtqueue_get_avail(vq);