Re: [PATCH v2] net/virtio_user: fix issue with converting cq descriptor IOVA address to VA

[David Marchand <david.marchand@redhat.com>]

On Thu, Jul 11, 2024 at 2:44 PM Srujana Challa <schalla@marvell.com> wrote:
>
> This patch modifies the code to convert descriptor buffer IOVA
> addresses to virtual addresses only when use_va flag is false.
>
> This patch resolves a segmentation fault with the vhost-user backend
> that occurs during the processing of the shadow control queue.
>
> 'Fixes: 67e9e504dae2 ("net/virtio_user: convert cq descriptor IOVA
> address to Virtual address")'

No single quote around the Fixes: tag, and on a single line please.

As for the title, how about: "net/virtio_user: fix cq descriptor
conversion with non vDPA backend" ?

>
> Reported-by: David Marchand <david.marchand@redhat.com>
> Signed-off-by: Srujana Challa <schalla@marvell.com>
> ---
> v2:
> - Added Reported-by tag.
>
>  .../net/virtio/virtio_user/virtio_user_dev.c  | 28 +++++++++++--------
>  1 file changed, 16 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> index fed66d2ae9..94e0ddcb94 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> @@ -905,12 +905,12 @@ virtio_user_handle_mq(struct virtio_user_dev *dev, uint16_t q_pairs)
>  #define CVQ_MAX_DATA_DESCS 32
>
>  static inline void *
> -virtio_user_iova2virt(rte_iova_t iova)
> +virtio_user_iova2virt(rte_iova_t iova, bool use_va)

All the code in this file passes the virtio_user_dev object, please
keep this convention.

IOW:
-virtio_user_iova2virt(rte_iova_t iova)
+virtio_user_iova2virt(struct virtio_user_dev *dev, rte_iova_t iova)

>  {
> -       if (rte_eal_iova_mode() == RTE_IOVA_VA)
> -               return (void *)(uintptr_t)iova;
> -       else
> +       if (rte_eal_iova_mode() == RTE_IOVA_PA && !use_va)
>                 return rte_mem_iova2virt(iova);
> +       else
> +               return (void *)(uintptr_t)iova;

Why do we need to invert this test?

I would make the change as simple as:
-       if (rte_eal_iova_mode() == RTE_IOVA_VA)
+       if (rte_eal_iova_mode() == RTE_IOVA_VA || dev->hw.use_va)


>  }
>
>  static uint32_t
> @@ -922,6 +922,7 @@ virtio_user_handle_ctrl_msg_split(struct virtio_user_dev *dev, struct vring *vri
>         uint16_t i, idx_data, idx_status;
>         uint32_t n_descs = 0;
>         int dlen[CVQ_MAX_DATA_DESCS], nb_dlen = 0;
> +       bool use_va = dev->hw.use_va;
>
>         /* locate desc for header, data, and status */
>         idx_data = vring->desc[idx_hdr].next;
> @@ -938,18 +939,18 @@ virtio_user_handle_ctrl_msg_split(struct virtio_user_dev *dev, struct vring *vri
>         idx_status = i;
>         n_descs++;
>
> -       hdr = virtio_user_iova2virt(vring->desc[idx_hdr].addr);
> +       hdr = virtio_user_iova2virt(vring->desc[idx_hdr].addr, use_va);
>         if (hdr->class == VIRTIO_NET_CTRL_MQ &&
>             hdr->cmd == VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET) {
>                 uint16_t queues, *addr;
>
> -               addr = virtio_user_iova2virt(vring->desc[idx_data].addr);
> +               addr = virtio_user_iova2virt(vring->desc[idx_data].addr, use_va);
>                 queues = *addr;
>                 status = virtio_user_handle_mq(dev, queues);
>         } else if (hdr->class == VIRTIO_NET_CTRL_MQ && hdr->cmd == VIRTIO_NET_CTRL_MQ_RSS_CONFIG) {
>                 struct virtio_net_ctrl_rss *rss;
>
> -               rss = virtio_user_iova2virt(vring->desc[idx_data].addr);
> +               rss = virtio_user_iova2virt(vring->desc[idx_data].addr, use_va);
>                 status = virtio_user_handle_mq(dev, rss->max_tx_vq);
>         } else if (hdr->class == VIRTIO_NET_CTRL_RX  ||
>                    hdr->class == VIRTIO_NET_CTRL_MAC ||
> @@ -962,7 +963,8 @@ virtio_user_handle_ctrl_msg_split(struct virtio_user_dev *dev, struct vring *vri
>                                 (struct virtio_pmd_ctrl *)hdr, dlen, nb_dlen);
>
>         /* Update status */
> -       *(virtio_net_ctrl_ack *)virtio_user_iova2virt(vring->desc[idx_status].addr) = status;
> +       *(virtio_net_ctrl_ack *)
> +               virtio_user_iova2virt(vring->desc[idx_status].addr, use_va) = status;

Afaics, no need for reindenting.

>
>         return n_descs;
>  }
> @@ -987,6 +989,7 @@ virtio_user_handle_ctrl_msg_packed(struct virtio_user_dev *dev,
>         /* initialize to one, header is first */
>         uint32_t n_descs = 1;
>         int dlen[CVQ_MAX_DATA_DESCS], nb_dlen = 0;
> +       bool use_va = dev->hw.use_va;
>
>         /* locate desc for header, data, and status */
>         idx_data = idx_hdr + 1;
> @@ -1004,18 +1007,18 @@ virtio_user_handle_ctrl_msg_packed(struct virtio_user_dev *dev,
>                 n_descs++;
>         }
>
> -       hdr = virtio_user_iova2virt(vring->desc[idx_hdr].addr);
> +       hdr = virtio_user_iova2virt(vring->desc[idx_hdr].addr, use_va);
>         if (hdr->class == VIRTIO_NET_CTRL_MQ &&
>             hdr->cmd == VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET) {
>                 uint16_t queues, *addr;
>
> -               addr = virtio_user_iova2virt(vring->desc[idx_data].addr);
> +               addr = virtio_user_iova2virt(vring->desc[idx_data].addr, use_va);
>                 queues = *addr;
>                 status = virtio_user_handle_mq(dev, queues);
>         } else if (hdr->class == VIRTIO_NET_CTRL_MQ && hdr->cmd == VIRTIO_NET_CTRL_MQ_RSS_CONFIG) {
>                 struct virtio_net_ctrl_rss *rss;
>
> -               rss = virtio_user_iova2virt(vring->desc[idx_data].addr);
> +               rss = virtio_user_iova2virt(vring->desc[idx_data].addr, use_va);
>                 status = virtio_user_handle_mq(dev, rss->max_tx_vq);
>         } else if (hdr->class == VIRTIO_NET_CTRL_RX  ||
>                    hdr->class == VIRTIO_NET_CTRL_MAC ||
> @@ -1028,7 +1031,8 @@ virtio_user_handle_ctrl_msg_packed(struct virtio_user_dev *dev,
>                                 (struct virtio_pmd_ctrl *)hdr, dlen, nb_dlen);
>
>         /* Update status */
> -       *(virtio_net_ctrl_ack *)virtio_user_iova2virt(vring->desc[idx_status].addr) = status;
> +       *(virtio_net_ctrl_ack *)
> +               virtio_user_iova2virt(vring->desc[idx_status].addr, use_va) = status;

Idem, no reindenting.

>
>         /* Update used descriptor */
>         vring->desc[idx_hdr].id = vring->desc[idx_status].id;
> --
> 2.25.1
>


-- 
David Marchand