Re: [RFC PATCH 2/5] virtio-net: Added property to load eBPF RSS with fds.

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Mar 30, 2023 at 03:15:19AM +0300, Andrew Melnychenko wrote:
> eBPF RSS program and maps may now be passed during initialization.
> Initially was implemented for libvirt to launch qemu without permissions,
> and initialized eBPF program through the helper.
> 
> Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
> ---
>  hw/net/virtio-net.c            | 77 ++++++++++++++++++++++++++++++++--
>  include/hw/virtio/virtio-net.h |  1 +
>  2 files changed, 74 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 53e1c32643..45d448a83d 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -42,6 +42,7 @@
>  #include "sysemu/sysemu.h"
>  #include "trace.h"
>  #include "monitor/qdev.h"
> +#include "monitor/monitor.h"
>  #include "hw/pci/pci_device.h"
>  #include "net_rx_pkt.h"
>  #include "hw/virtio/vhost.h"
> @@ -1305,14 +1306,81 @@ static void virtio_net_detach_epbf_rss(VirtIONet *n)
>      virtio_net_attach_ebpf_to_backend(n->nic, -1);
>  }
>  
> -static bool virtio_net_load_ebpf(VirtIONet *n)
> +static int virtio_net_get_ebpf_rss_fds(char *str, char *fds[], int nfds)

Needs to have an 'Error **errp' parameter

> +{
> +    char *ptr = str;
> +    char *cur = NULL;
> +    size_t len = strlen(str);
> +    int i = 0;
> +
> +    for (; i < nfds && ptr < str + len;) {
> +        cur = strchr(ptr, ':');
> +
> +        if (cur == NULL) {
> +            fds[i] = g_strdup(ptr);
> +        } else {
> +            fds[i] = g_strndup(ptr, cur - ptr);
> +        }
> +
> +        i++;
> +        if (cur == NULL) {
> +            break;
> +        } else {
> +            ptr = cur + 1;
> +        }
> +    }

...and here needs to error_setg(...) if the string being parsed has
more FDs present than 'nfds', and return error.

It should also report error if less than 'nfds' were present.

> +
> +    return i;
> +}
> +
> +static bool virtio_net_load_ebpf_fds(VirtIONet *n)
>  {
> -    if (!virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
> -        /* backend does't support steering ebpf */
> +    char *fds_strs[EBPF_RSS_MAX_FDS];
> +    int fds[EBPF_RSS_MAX_FDS];
> +    int nfds;
> +    int ret = false;
> +    Error *errp;

This method should be having 'Error **errp' passed into it
instead

> +    int i = 0;
> +
> +    if (n == NULL || !n->ebpf_rss_fds) {
>          return false;
>      }

The only caller has already de-referenced 'n' so n == NULL is
impossible. The caller has also chck ebpf_rss_fds != NULL.
IOW, this is redundant

> -    return ebpf_rss_load(&n->ebpf_rss);
> +    nfds = virtio_net_get_ebpf_rss_fds(n->ebpf_rss_fds,
> +                                       fds_strs, EBPF_RSS_MAX_FDS);

Needs to pass in 'errp' and check for the error condition on return

  if (nfds != EBPF_RSS_MAX_FDS)
      return false;

> +    for (i = 0; i < nfds; i++) {
> +        fds[i] = monitor_fd_param(monitor_cur(), fds_strs[i], &errp);

if (fds[i] < 0)
   ....close all FDs so far and return error...


> +    }
> +
> +    if (nfds == EBPF_RSS_MAX_FDS) {
> +        ret = ebpf_rss_load_fds(&n->ebpf_rss, fds[0], fds[1], fds[2], fds[3]);
> +    }

This condition is not required, since we should have check
it immediately after the virtio_net_get_ebpf_rss_fds() call


> +
> +    if (!ret) {
> +        for (i = 0; i < nfds; i++) {
> +            close(fds[i]);
> +        }
> +    }
> +
> +    for (i = 0; i < nfds; i++) {
> +        g_free(fds_strs[i]);
> +    }
> +
> +    return ret;
> +}
> +
> +static bool virtio_net_load_ebpf(VirtIONet *n)

This needs to have "Error **errp' added to it and return an
error on failure. The caller already has an 'errp' available
to pass in.

> +{
> +    bool ret = true;
> +
> +    if (virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
> +        if (!(n->ebpf_rss_fds
> +                && virtio_net_load_ebpf_fds(n))) {
> +            ret = ebpf_rss_load(&n->ebpf_rss);
> +        }
> +    }
> +
> +    return ret;
>  }
>  
>  static void virtio_net_unload_ebpf(VirtIONet *n)
> @@ -3900,6 +3968,7 @@ static Property virtio_net_properties[] = {
>                      VIRTIO_NET_F_RSS, false),
>      DEFINE_PROP_BIT64("hash", VirtIONet, host_features,
>                      VIRTIO_NET_F_HASH_REPORT, false),
> +    DEFINE_PROP_STRING("ebpf_rss_fds", VirtIONet, ebpf_rss_fds),
>      DEFINE_PROP_BIT64("guest_rsc_ext", VirtIONet, host_features,
>                      VIRTIO_NET_F_RSC_EXT, false),
>      DEFINE_PROP_UINT32("rsc_interval", VirtIONet, rsc_timeout,
> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> index ef234ffe7e..e10ce88f91 100644
> --- a/include/hw/virtio/virtio-net.h
> +++ b/include/hw/virtio/virtio-net.h
> @@ -219,6 +219,7 @@ struct VirtIONet {
>      VirtioNetRssData rss_data;
>      struct NetRxPkt *rx_pkt;
>      struct EBPFRSSContext ebpf_rss;
> +    char *ebpf_rss_fds;
>  };
>  
>  size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,
> -- 
> 2.39.1
> 

With regards,
Daniel
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