netdev - [PATCH v12 14/40] virtio_ring: split: introduce virtqueue_resize

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Message-Id: <20220720030436.79520-15-xuanzhuo@linux.alibaba.com>
Date:   Wed, 20 Jul 2022 11:04:10 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     virtualization@...ts.linux-foundation.org
Cc:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Vadim Pasternak <vadimp@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, bpf@...r.kernel.org,
        kangjie.xu@...ux.alibaba.com
Subject: [PATCH v12 14/40] virtio_ring: split: introduce virtqueue_resize_split()

virtio ring split supports resize.

Only after the new vring is successfully allocated based on the new num,
we will release the old vring. In any case, an error is returned,
indicating that the vring still points to the old vring.

In the case of an error, re-initialize(virtqueue_reinit_split()) the
virtqueue to ensure that the vring can be used.

In addition, vring_align, may_reduce_num are necessary for reallocating
vring, so they are retained for creating vq.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Acked-by: Jason Wang <jasowang@...hat.com>
---
 drivers/virtio/virtio_ring.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 6de1129e2aa6..2ea6d022cbd7 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -212,6 +212,7 @@ struct vring_virtqueue {
 };
 
 static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
+static void vring_free(struct virtqueue *_vq);
 
 /*
  * Helpers.
@@ -1115,6 +1116,38 @@ static struct virtqueue *vring_create_virtqueue_split(
 	return vq;
 }
 
+static int virtqueue_resize_split(struct virtqueue *_vq, u32 num)
+{
+	struct vring_virtqueue_split vring_split = {};
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	struct virtio_device *vdev = _vq->vdev;
+	int err;
+
+	err = vring_alloc_queue_split(&vring_split, vdev, num,
+				      vq->split.vring_align,
+				      vq->split.may_reduce_num);
+	if (err)
+		goto err;
+
+	err = vring_alloc_state_extra_split(&vring_split);
+	if (err) {
+		vring_free_split(&vring_split, vdev);
+		goto err;
+	}
+
+	vring_free(&vq->vq);
+
+	virtqueue_init(vq, vring_split.vring.num);
+	virtqueue_vring_attach_split(vq, &vring_split);
+	virtqueue_vring_init_split(vq);
+
+	return 0;
+
+err:
+	virtqueue_reinit_split(vq);
+	return -ENOMEM;
+}
+
 
 /*
  * Packed ring specific functions - *_packed().
-- 
2.31.0