Re: [PATCH] migration/rdma: Remove qemu_rdma_broken_ipv6_kernel

[Fabiano Rosas <farosas@suse.de>]

Jack Wang <jinpu.wang@ionos.com> writes:

> I hit following error which testing migration in pure RoCE env:
> "-incoming rdma:[::]:8089: RDMA ERROR: You only have RoCE / iWARP devices in your
> systems and your management software has specified '[::]', but IPv6 over RoCE /
> iWARP is not supported in Linux.#012'."
>
> In our setup, we use rdma bind on ipv6 on target host, while connect from source
> with ipv4, remove the qemu_rdma_broken_ipv6_kernel, migration just work
> fine.
>
> Checking the git history, the function was added since introducing of
> rdma migration, which is more than 10 years ago. linux-rdma has
> improved support on RoCE/iWARP for ipv6 over past years. There are a few fixes
> back in 2016 seems related to the issue, eg:
> aeb76df46d11 ("IB/core: Set routable RoCE gid type for ipv4/ipv6 networks")
>
> other fixes back in 2018, eg:
> 052eac6eeb56 RDMA/cma: Update RoCE multicast routines to use net namespace
> 8d20a1f0ecd5 RDMA/cma: Fix rdma_cm raw IB path setting for RoCE
> 9327c7afdce3 RDMA/cma: Provide a function to set RoCE path record L2 parameters
> 5c181bda77f4 RDMA/cma: Set default GID type as RoCE when resolving RoCE route
> 3c7f67d1880d IB/cma: Fix default RoCE type setting
> be1d325a3358 IB/core: Set RoCEv2 MGID according to spec
> 63a5f483af0e IB/cma: Set default gid type to RoCEv2
>
> So remove the outdated function and it's usage.
>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Li Zhijian <lizhijian@fujitsu.com>
> Cc: Yu Zhang <yu.zhang@ionos.com>
> Cc: qemu-devel@nongnu.org
> Cc: linux-rdma@vger.kernel.org
> Cc: michael@flatgalaxy.com
> Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
> Tested-by: Li zhijian <lizhijian@fujitsu.com>
> Reviewed-by: Michael Galaxy <mrgalaxy@nvidia.com>
> ---
> v1: drop RFC, fix build error (zhijian), collect Reviewed-by and Tested-by
>
>  migration/rdma.c | 159 -----------------------------------------------
>  1 file changed, 159 deletions(-)
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 76fb0349238a..e228520b8e01 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -767,149 +767,6 @@ static void qemu_rdma_dump_gid(const char *who, struct rdma_cm_id *id)
>      trace_qemu_rdma_dump_gid(who, sgid, dgid);
>  }
>  
> -/*
> - * As of now, IPv6 over RoCE / iWARP is not supported by linux.
> - * We will try the next addrinfo struct, and fail if there are
> - * no other valid addresses to bind against.
> - *
> - * If user is listening on '[::]', then we will not have a opened a device
> - * yet and have no way of verifying if the device is RoCE or not.
> - *
> - * In this case, the source VM will throw an error for ALL types of
> - * connections (both IPv4 and IPv6) if the destination machine does not have
> - * a regular infiniband network available for use.
> - *
> - * The only way to guarantee that an error is thrown for broken kernels is
> - * for the management software to choose a *specific* interface at bind time
> - * and validate what time of hardware it is.
> - *
> - * Unfortunately, this puts the user in a fix:
> - *
> - *  If the source VM connects with an IPv4 address without knowing that the
> - *  destination has bound to '[::]' the migration will unconditionally fail
> - *  unless the management software is explicitly listening on the IPv4
> - *  address while using a RoCE-based device.
> - *
> - *  If the source VM connects with an IPv6 address, then we're OK because we can
> - *  throw an error on the source (and similarly on the destination).
> - *
> - *  But in mixed environments, this will be broken for a while until it is fixed
> - *  inside linux.
> - *
> - * We do provide a *tiny* bit of help in this function: We can list all of the
> - * devices in the system and check to see if all the devices are RoCE or
> - * Infiniband.
> - *
> - * If we detect that we have a *pure* RoCE environment, then we can safely
> - * thrown an error even if the management software has specified '[::]' as the
> - * bind address.
> - *
> - * However, if there is are multiple hetergeneous devices, then we cannot make
> - * this assumption and the user just has to be sure they know what they are
> - * doing.
> - *
> - * Patches are being reviewed on linux-rdma.
> - */
> -static int qemu_rdma_broken_ipv6_kernel(struct ibv_context *verbs, Error **errp)
> -{
> -    /* This bug only exists in linux, to our knowledge. */
> -#ifdef CONFIG_LINUX
> -    struct ibv_port_attr port_attr;
> -
> -    /*
> -     * Verbs are only NULL if management has bound to '[::]'.
> -     *
> -     * Let's iterate through all the devices and see if there any pure IB
> -     * devices (non-ethernet).
> -     *
> -     * If not, then we can safely proceed with the migration.
> -     * Otherwise, there are no guarantees until the bug is fixed in linux.
> -     */
> -    if (!verbs) {
> -        int num_devices;
> -        struct ibv_device **dev_list = ibv_get_device_list(&num_devices);
> -        bool roce_found = false;
> -        bool ib_found = false;
> -
> -        for (int x = 0; x < num_devices; x++) {
> -            verbs = ibv_open_device(dev_list[x]);
> -            /*
> -             * ibv_open_device() is not documented to set errno.  If
> -             * it does, it's somebody else's doc bug.  If it doesn't,
> -             * the use of errno below is wrong.
> -             * TODO Find out whether ibv_open_device() sets errno.
> -             */
> -            if (!verbs) {
> -                if (errno == EPERM) {
> -                    continue;
> -                } else {
> -                    error_setg_errno(errp, errno,
> -                                     "could not open RDMA device context");
> -                    return -1;
> -                }
> -            }
> -
> -            if (ibv_query_port(verbs, 1, &port_attr)) {
> -                ibv_close_device(verbs);
> -                error_setg(errp,
> -                           "RDMA ERROR: Could not query initial IB port");
> -                return -1;
> -            }
> -
> -            if (port_attr.link_layer == IBV_LINK_LAYER_INFINIBAND) {
> -                ib_found = true;
> -            } else if (port_attr.link_layer == IBV_LINK_LAYER_ETHERNET) {
> -                roce_found = true;
> -            }
> -
> -            ibv_close_device(verbs);
> -
> -        }
> -
> -        if (roce_found) {
> -            if (ib_found) {
> -                warn_report("migrations may fail:"
> -                            " IPv6 over RoCE / iWARP in linux"
> -                            " is broken. But since you appear to have a"
> -                            " mixed RoCE / IB environment, be sure to only"
> -                            " migrate over the IB fabric until the kernel "
> -                            " fixes the bug.");
> -            } else {
> -                error_setg(errp, "RDMA ERROR: "
> -                           "You only have RoCE / iWARP devices in your systems"
> -                           " and your management software has specified '[::]'"
> -                           ", but IPv6 over RoCE / iWARP is not supported in Linux.");
> -                return -1;
> -            }
> -        }
> -
> -        return 0;
> -    }
> -
> -    /*
> -     * If we have a verbs context, that means that some other than '[::]' was
> -     * used by the management software for binding. In which case we can
> -     * actually warn the user about a potentially broken kernel.
> -     */
> -
> -    /* IB ports start with 1, not 0 */
> -    if (ibv_query_port(verbs, 1, &port_attr)) {
> -        error_setg(errp, "RDMA ERROR: Could not query initial IB port");
> -        return -1;
> -    }
> -
> -    if (port_attr.link_layer == IBV_LINK_LAYER_ETHERNET) {
> -        error_setg(errp, "RDMA ERROR: "
> -                   "Linux kernel's RoCE / iWARP does not support IPv6 "
> -                   "(but patches on linux-rdma in progress)");
> -        return -1;
> -    }
> -
> -#endif
> -
> -    return 0;
> -}
> -
>  /*
>   * Figure out which RDMA device corresponds to the requested IP hostname
>   * Also create the initial connection manager identifiers for opening
> @@ -955,7 +812,6 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
>  
>      /* Try all addresses, saving the first error in @err */
>      for (struct rdma_addrinfo *e = res; e != NULL; e = e->ai_next) {
> -        Error **local_errp = err ? NULL : &err;
>  
>          inet_ntop(e->ai_family,
>              &((struct sockaddr_in *) e->ai_dst_addr)->sin_addr, ip, sizeof ip);
> @@ -964,13 +820,6 @@ static int qemu_rdma_resolve_host(RDMAContext *rdma, Error **errp)
>          ret = rdma_resolve_addr(rdma->cm_id, NULL, e->ai_dst_addr,
>                  RDMA_RESOLVE_TIMEOUT_MS);
>          if (ret >= 0) {
> -            if (e->ai_family == AF_INET6) {
> -                ret = qemu_rdma_broken_ipv6_kernel(rdma->cm_id->verbs,
> -                                                   local_errp);
> -                if (ret < 0) {
> -                    continue;
> -                }
> -            }
>              error_free(err);

err is now unused and should be removed entirely. The comment before the
loop needs touching up as well.

>              goto route;
>          }
> @@ -2663,7 +2512,6 @@ static int qemu_rdma_dest_init(RDMAContext *rdma, Error **errp)
>  
>      /* Try all addresses, saving the first error in @err */
>      for (e = res; e != NULL; e = e->ai_next) {
> -        Error **local_errp = err ? NULL : &err;
>  
>          inet_ntop(e->ai_family,
>              &((struct sockaddr_in *) e->ai_dst_addr)->sin_addr, ip, sizeof ip);
> @@ -2672,13 +2520,6 @@ static int qemu_rdma_dest_init(RDMAContext *rdma, Error **errp)
>          if (ret < 0) {
>              continue;
>          }
> -        if (e->ai_family == AF_INET6) {
> -            ret = qemu_rdma_broken_ipv6_kernel(listen_id->verbs,
> -                                               local_errp);
> -            if (ret < 0) {
> -                continue;
> -            }
> -        }
>          error_free(err);

Same here.

>          break;
>      }