Re: [PULL 08/83] vdpa: Restore hash calculation state

[Stefan Hajnoczi]

On Wed, 18 Oct 2023 at 08:56, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Hawkins Jiawei <yin31149@gmail.com>
>
> This patch introduces vhost_vdpa_net_load_rss() to restore
> the hash calculation state at device's startup.
>
> Note that vhost_vdpa_net_load_rss() has `do_rss` argument,
> which allows future code to reuse this function to restore
> the receive-side scaling state when the VIRTIO_NET_F_RSS
> feature is enabled in SVQ. Currently, vhost_vdpa_net_load_rss()
> could only be invoked when `do_rss` is set to false.
>
> Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
> Message-Id: 
> <f5ffad10699001107022851e0560cb394039d6b0.1693297766.git.yin31149@gmail.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  net/vhost-vdpa.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 91 insertions(+)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 4b7c3b81b8..40d0bcbc0b 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -817,6 +817,88 @@ static int vhost_vdpa_net_load_mac(VhostVDPAState *s, 
> const VirtIONet *n,
>      return 0;
>  }
>
> +static int vhost_vdpa_net_load_rss(VhostVDPAState *s, const VirtIONet *n,
> +                                   struct iovec *out_cursor,
> +                                   struct iovec *in_cursor, bool do_rss)
> +{
> +    struct virtio_net_rss_config cfg;
> +    ssize_t r;
> +    g_autofree uint16_t *table = NULL;
> +
> +    /*
> +     * According to VirtIO standard, "Initially the device has all hash
> +     * types disabled and reports only VIRTIO_NET_HASH_REPORT_NONE.".
> +     *
> +     * Therefore, there is no need to send this CVQ command if the
> +     * driver disable the all hash types, which aligns with
> +     * the device's defaults.
> +     *
> +     * Note that the device's defaults can mismatch the driver's
> +     * configuration only at live migration.
> +     */
> +    if (!n->rss_data.enabled ||
> +        n->rss_data.hash_types == VIRTIO_NET_HASH_REPORT_NONE) {
> +        return 0;
> +    }
> +
> +    cfg.hash_types = cpu_to_le32(n->rss_data.hash_types);
> +
> +    /*
> +     * According to VirtIO standard, "Field reserved MUST contain zeroes.
> +     * It is defined to make the structure to match the layout of
> +     * virtio_net_rss_config structure, defined in 5.1.6.5.7.".
> +     *
> +     * Therefore, we need to zero the fields in struct virtio_net_rss_config,
> +     * which corresponds the `reserved` field in
> +     * struct virtio_net_hash_config.
> +     */
> +    memset(&cfg.indirection_table_mask, 0,
> +           sizeof_field(struct virtio_net_hash_config, reserved));

Please take a look at the following CI failure:

In file included from /usr/include/string.h:495,
from 
/home/gitlab-runner/builds/-LCfcJ2T/0/qemu-project/qemu/include/qemu/osdep.h:116,
from ../net/vhost-vdpa.c:12:
In function ‘memset’,
inlined from ‘vhost_vdpa_net_load_rss’ at ../net/vhost-vdpa.c:874:9:
/usr/include/s390x-linux-gnu/bits/string_fortified.h:71:10: error:
‘__builtin_memset’ offset [7, 12] from the object at ‘cfg’ is out of
the bounds of referenced subobject ‘indirection_table_mask’ with type
‘short unsigned int’ at offset 4 [-Werror=array-bounds]
71 | return __builtin___memset_chk (__dest, __ch, __len, __bos0 (__dest));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

https://gitlab.com/qemu-project/qemu/-/jobs/5329820077

> +
> +    table = g_malloc_n(n->rss_data.indirections_len,
> +                       sizeof(n->rss_data.indirections_table[0]));
> +    for (int i = 0; i < n->rss_data.indirections_len; ++i) {
> +        table[i] = cpu_to_le16(n->rss_data.indirections_table[i]);
> +    }
> +
> +    /*
> +     * Consider that virtio_net_handle_rss() currently does not restore the
> +     * hash key length parsed from the CVQ command sent from the guest into
> +     * n->rss_data and uses the maximum key length in other code, so we also
> +     * employthe the maxium key length here.
> +     */
> +    cfg.hash_key_length = sizeof(n->rss_data.key);
> +
> +    const struct iovec data[] = {
> +        {
> +            .iov_base = &cfg,
> +            .iov_len = offsetof(struct virtio_net_rss_config,
> +                                indirection_table),
> +        }, {
> +            .iov_base = table,
> +            .iov_len = n->rss_data.indirections_len *
> +                       sizeof(n->rss_data.indirections_table[0]),
> +        }, {
> +            .iov_base = &cfg.max_tx_vq,
> +            .iov_len = offsetof(struct virtio_net_rss_config, hash_key_data) 
> -
> +                       offsetof(struct virtio_net_rss_config, max_tx_vq),
> +        }, {
> +            .iov_base = (void *)n->rss_data.key,
> +            .iov_len = sizeof(n->rss_data.key),
> +        }
> +    };
> +
> +    r = vhost_vdpa_net_load_cmd(s, out_cursor, in_cursor,
> +                                VIRTIO_NET_CTRL_MQ,
> +                                VIRTIO_NET_CTRL_MQ_HASH_CONFIG,
> +                                data, ARRAY_SIZE(data));
> +    if (unlikely(r < 0)) {
> +        return r;
> +    }
> +
> +    return 0;
> +}
> +
>  static int vhost_vdpa_net_load_mq(VhostVDPAState *s,
>                                    const VirtIONet *n,
>                                    struct iovec *out_cursor,
> @@ -842,6 +924,15 @@ static int vhost_vdpa_net_load_mq(VhostVDPAState *s,
>          return r;
>      }
>
> +    if (!virtio_vdev_has_feature(&n->parent_obj, VIRTIO_NET_F_HASH_REPORT)) {
> +        return 0;
> +    }
> +
> +    r = vhost_vdpa_net_load_rss(s, n, out_cursor, in_cursor, false);
> +    if (unlikely(r < 0)) {
> +        return r;
> +    }
> +
>      return 0;
>  }
>
> --
> MST
>
>