Re: [PATCH RESEND V2 3/3] vdpa/mlx5: Use consistent RQT size

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Apr 04, 2022 at 11:07:36AM +0000, Eli Cohen wrote:
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Monday, April 4, 2022 1:35 PM
> > To: Jason Wang <jasowang@redhat.com>
> > Cc: Eli Cohen <elic@nvidia.com>; hdanton@sina.com; virtualization@lists.linux-foundation.org; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH RESEND V2 3/3] vdpa/mlx5: Use consistent RQT size
> > 
> > On Tue, Mar 29, 2022 at 12:21:09PM +0800, Jason Wang wrote:
> > > From: Eli Cohen <elic@nvidia.com>
> > >
> > > The current code evaluates RQT size based on the configured number of
> > > virtqueues. This can raise an issue in the following scenario:
> > >
> > > Assume MQ was negotiated.
> > > 1. mlx5_vdpa_set_map() gets called.
> > > 2. handle_ctrl_mq() is called setting cur_num_vqs to some value, lower
> > >    than the configured max VQs.
> > > 3. A second set_map gets called, but now a smaller number of VQs is used
> > >    to evaluate the size of the RQT.
> > > 4. handle_ctrl_mq() is called with a value larger than what the RQT can
> > >    hold. This will emit errors and the driver state is compromised.
> > >
> > > To fix this, we use a new field in struct mlx5_vdpa_net to hold the
> > > required number of entries in the RQT. This value is evaluated in
> > > mlx5_vdpa_set_driver_features() where we have the negotiated features
> > > all set up.
> > >
> > > In addtion
> > 
> > addition?
> 
> Do you need me to send another version?

It's a bit easier that way but I can handle it manually too.

> If so, let's wait for Jason's reply.

Right.

> > 
> > > to that, we take into consideration the max capability of RQT
> > > entries early when the device is added so we don't need to take consider
> > > it when creating the RQT.
> > >
> > > Last, we remove the use of mlx5_vdpa_max_qps() which just returns the
> > > max_vas / 2 and make the code clearer.
> > >
> > > Fixes: 52893733f2c5 ("vdpa/mlx5: Add multiqueue support")
> > > Signed-off-by: Eli Cohen <elic@nvidia.com>
> > 
> > Jason I don't have your ack or S.O.B on this one.
> > 
> > 
> > > ---
> > >  drivers/vdpa/mlx5/net/mlx5_vnet.c | 61 +++++++++++--------------------
> > >  1 file changed, 21 insertions(+), 40 deletions(-)
> > >
> > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > index 53b8c1a68f90..61bec1ed0bc9 100644
> > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > @@ -161,6 +161,7 @@ struct mlx5_vdpa_net {
> > >  	struct mlx5_flow_handle *rx_rule_mcast;
> > >  	bool setup;
> > >  	u32 cur_num_vqs;
> > > +	u32 rqt_size;
> > >  	struct notifier_block nb;
> > >  	struct vdpa_callback config_cb;
> > >  	struct mlx5_vdpa_wq_ent cvq_ent;
> > > @@ -204,17 +205,12 @@ static __virtio16 cpu_to_mlx5vdpa16(struct mlx5_vdpa_dev *mvdev, u16 val)
> > >  	return __cpu_to_virtio16(mlx5_vdpa_is_little_endian(mvdev), val);
> > >  }
> > >
> > > -static inline u32 mlx5_vdpa_max_qps(int max_vqs)
> > > -{
> > > -	return max_vqs / 2;
> > > -}
> > > -
> > >  static u16 ctrl_vq_idx(struct mlx5_vdpa_dev *mvdev)
> > >  {
> > >  	if (!(mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_MQ)))
> > >  		return 2;
> > >
> > > -	return 2 * mlx5_vdpa_max_qps(mvdev->max_vqs);
> > > +	return mvdev->max_vqs;
> > >  }
> > >
> > >  static bool is_ctrl_vq_idx(struct mlx5_vdpa_dev *mvdev, u16 idx)
> > > @@ -1236,25 +1232,13 @@ static void teardown_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *
> > >  static int create_rqt(struct mlx5_vdpa_net *ndev)
> > >  {
> > >  	__be32 *list;
> > > -	int max_rqt;
> > >  	void *rqtc;
> > >  	int inlen;
> > >  	void *in;
> > >  	int i, j;
> > >  	int err;
> > > -	int num;
> > > -
> > > -	if (!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_MQ)))
> > > -		num = 1;
> > > -	else
> > > -		num = ndev->cur_num_vqs / 2;
> > >
> > > -	max_rqt = min_t(int, roundup_pow_of_two(num),
> > > -			1 << MLX5_CAP_GEN(ndev->mvdev.mdev, log_max_rqt_size));
> > > -	if (max_rqt < 1)
> > > -		return -EOPNOTSUPP;
> > > -
> > > -	inlen = MLX5_ST_SZ_BYTES(create_rqt_in) + max_rqt * MLX5_ST_SZ_BYTES(rq_num);
> > > +	inlen = MLX5_ST_SZ_BYTES(create_rqt_in) + ndev->rqt_size * MLX5_ST_SZ_BYTES(rq_num);
> > >  	in = kzalloc(inlen, GFP_KERNEL);
> > >  	if (!in)
> > >  		return -ENOMEM;
> > > @@ -1263,12 +1247,12 @@ static int create_rqt(struct mlx5_vdpa_net *ndev)
> > >  	rqtc = MLX5_ADDR_OF(create_rqt_in, in, rqt_context);
> > >
> > >  	MLX5_SET(rqtc, rqtc, list_q_type, MLX5_RQTC_LIST_Q_TYPE_VIRTIO_NET_Q);
> > > -	MLX5_SET(rqtc, rqtc, rqt_max_size, max_rqt);
> > > +	MLX5_SET(rqtc, rqtc, rqt_max_size, ndev->rqt_size);
> > >  	list = MLX5_ADDR_OF(rqtc, rqtc, rq_num[0]);
> > > -	for (i = 0, j = 0; i < max_rqt; i++, j += 2)
> > > -		list[i] = cpu_to_be32(ndev->vqs[j % (2 * num)].virtq_id);
> > > +	for (i = 0, j = 0; i < ndev->rqt_size; i++, j += 2)
> > > +		list[i] = cpu_to_be32(ndev->vqs[j % ndev->cur_num_vqs].virtq_id);
> > >
> > > -	MLX5_SET(rqtc, rqtc, rqt_actual_size, max_rqt);
> > > +	MLX5_SET(rqtc, rqtc, rqt_actual_size, ndev->rqt_size);
> > >  	err = mlx5_vdpa_create_rqt(&ndev->mvdev, in, inlen, &ndev->res.rqtn);
> > >  	kfree(in);
> > >  	if (err)
> > > @@ -1282,19 +1266,13 @@ static int create_rqt(struct mlx5_vdpa_net *ndev)
> > >  static int modify_rqt(struct mlx5_vdpa_net *ndev, int num)
> > >  {
> > >  	__be32 *list;
> > > -	int max_rqt;
> > >  	void *rqtc;
> > >  	int inlen;
> > >  	void *in;
> > >  	int i, j;
> > >  	int err;
> > >
> > > -	max_rqt = min_t(int, roundup_pow_of_two(ndev->cur_num_vqs / 2),
> > > -			1 << MLX5_CAP_GEN(ndev->mvdev.mdev, log_max_rqt_size));
> > > -	if (max_rqt < 1)
> > > -		return -EOPNOTSUPP;
> > > -
> > > -	inlen = MLX5_ST_SZ_BYTES(modify_rqt_in) + max_rqt * MLX5_ST_SZ_BYTES(rq_num);
> > > +	inlen = MLX5_ST_SZ_BYTES(modify_rqt_in) + ndev->rqt_size * MLX5_ST_SZ_BYTES(rq_num);
> > >  	in = kzalloc(inlen, GFP_KERNEL);
> > >  	if (!in)
> > >  		return -ENOMEM;
> > > @@ -1305,10 +1283,10 @@ static int modify_rqt(struct mlx5_vdpa_net *ndev, int num)
> > >  	MLX5_SET(rqtc, rqtc, list_q_type, MLX5_RQTC_LIST_Q_TYPE_VIRTIO_NET_Q);
> > >
> > >  	list = MLX5_ADDR_OF(rqtc, rqtc, rq_num[0]);
> > > -	for (i = 0, j = 0; i < max_rqt; i++, j += 2)
> > > +	for (i = 0, j = 0; i < ndev->rqt_size; i++, j += 2)
> > >  		list[i] = cpu_to_be32(ndev->vqs[j % num].virtq_id);
> > >
> > > -	MLX5_SET(rqtc, rqtc, rqt_actual_size, max_rqt);
> > > +	MLX5_SET(rqtc, rqtc, rqt_actual_size, ndev->rqt_size);
> > >  	err = mlx5_vdpa_modify_rqt(&ndev->mvdev, in, inlen, ndev->res.rqtn);
> > >  	kfree(in);
> > >  	if (err)
> > > @@ -1582,7 +1560,7 @@ static virtio_net_ctrl_ack handle_ctrl_mq(struct mlx5_vdpa_dev *mvdev, u8 cmd)
> > >
> > >  		newqps = mlx5vdpa16_to_cpu(mvdev, mq.virtqueue_pairs);
> > >  		if (newqps < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN ||
> > > -		    newqps > mlx5_vdpa_max_qps(mvdev->max_vqs))
> > > +		    newqps > ndev->rqt_size)
> > >  			break;
> > >
> > >  		if (ndev->cur_num_vqs == 2 * newqps) {
> > > @@ -1946,7 +1924,7 @@ static int setup_virtqueues(struct mlx5_vdpa_dev *mvdev)
> > >  	int err;
> > >  	int i;
> > >
> > > -	for (i = 0; i < 2 * mlx5_vdpa_max_qps(mvdev->max_vqs); i++) {
> > > +	for (i = 0; i < mvdev->max_vqs; i++) {
> > >  		err = setup_vq(ndev, &ndev->vqs[i]);
> > >  		if (err)
> > >  			goto err_vq;
> > > @@ -2017,9 +1995,11 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
> > >
> > >  	ndev->mvdev.actual_features = features & ndev->mvdev.mlx_features;
> > >  	if (ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_MQ))
> > > -		ndev->cur_num_vqs = 2 * mlx5vdpa16_to_cpu(mvdev, ndev->config.max_virtqueue_pairs);
> > > +		ndev->rqt_size = mlx5vdpa16_to_cpu(mvdev, ndev->config.max_virtqueue_pairs);
> > >  	else
> > > -		ndev->cur_num_vqs = 2;
> > > +		ndev->rqt_size = 1;
> > > +
> > > +	ndev->cur_num_vqs = 2 * ndev->rqt_size;
> > >
> > >  	update_cvq_info(mvdev);
> > >  	return err;
> > > @@ -2486,7 +2466,7 @@ static void init_mvqs(struct mlx5_vdpa_net *ndev)
> > >  	struct mlx5_vdpa_virtqueue *mvq;
> > >  	int i;
> > >
> > > -	for (i = 0; i < 2 * mlx5_vdpa_max_qps(ndev->mvdev.max_vqs); ++i) {
> > > +	for (i = 0; i < ndev->mvdev.max_vqs; ++i) {
> > >  		mvq = &ndev->vqs[i];
> > >  		memset(mvq, 0, offsetof(struct mlx5_vdpa_virtqueue, ri));
> > >  		mvq->index = i;
> > > @@ -2606,7 +2586,8 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
> > >  		return -EOPNOTSUPP;
> > >  	}
> > >
> > > -	max_vqs = MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues);
> > > +	max_vqs = min_t(int, MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues),
> > > +			1 << MLX5_CAP_GEN(mdev, log_max_rqt_size));
> > >  	if (max_vqs < 2) {
> > >  		dev_warn(mdev->device,
> > >  			 "%d virtqueues are supported. At least 2 are required\n",
> > > @@ -2670,7 +2651,7 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
> > >  		ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_NET_F_MAC);
> > >  	}
> > >
> > > -	config->max_virtqueue_pairs = cpu_to_mlx5vdpa16(mvdev, mlx5_vdpa_max_qps(max_vqs));
> > > +	config->max_virtqueue_pairs = cpu_to_mlx5vdpa16(mvdev, max_vqs / 2);
> > >  	mvdev->vdev.dma_dev = &mdev->pdev->dev;
> > >  	err = mlx5_vdpa_alloc_resources(&ndev->mvdev);
> > >  	if (err)
> > > @@ -2697,7 +2678,7 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
> > >  	ndev->nb.notifier_call = event_handler;
> > >  	mlx5_notifier_register(mdev, &ndev->nb);
> > >  	mvdev->vdev.mdev = &mgtdev->mgtdev;
> > > -	err = _vdpa_register_device(&mvdev->vdev, 2 * mlx5_vdpa_max_qps(max_vqs) + 1);
> > > +	err = _vdpa_register_device(&mvdev->vdev, max_vqs + 1);
> > >  	if (err)
> > >  		goto err_reg;
> > >
> > > --
> > > 2.18.1

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