Cornelia Huck
2019-Apr-08 11:01 UTC
[RFC PATCH 01/12] virtio/s390: use vring_create_virtqueue
On Fri, 5 Apr 2019 01:16:11 +0200 Halil Pasic <pasic at linux.ibm.com> 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 <pasic at linux.ibm.com> > --- > 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);
Michael S. Tsirkin
2019-Apr-08 12:37 UTC
[RFC PATCH 01/12] virtio/s390: use vring_create_virtqueue
On Mon, Apr 08, 2019 at 01:01:28PM +0200, Cornelia Huck wrote:> On Fri, 5 Apr 2019 01:16:11 +0200 > Halil Pasic <pasic at linux.ibm.com> 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 <pasic at linux.ibm.com> > > --- > > 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.)Yes, pls do. Not too late for a bugfix to go into the current linux.> > + 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);
Reasonably Related Threads
- [PATCH 01/10] virtio/s390: use vring_create_virtqueue
- [PATCH v4] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support
- [PATCH v4] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support
- [PATCH 0/3] S390-virtio: Adjustments for three function implementations
- [PATCH 0/3] S390-virtio: Adjustments for three function implementations