[dpdk-dev] dpdk 2.0.0: Issue mapping mempool into guest using IVSHMEM

[Mauricio Vásquez]

Hi all,

I'm trying to map a mempool into a guest using the IVSHMEM library but the
mempool is not visible from the guest.

The code I'm running is quite simple, on the host I run a primary DPDK
process that creates the mempool, creates a metadata file and then adds the
mempool to it.

The code is:
...
int main(int argc, char * argv[])
{
    int retval = 0;

    /* Init EAL, parsing EAL args */
    retval = rte_eal_init(argc, argv);
    if (retval < 0)
        return -1;

    char cmdline[PATH_MAX] = {0};

    struct rte_mempool *packets_pool;
    //Create mempool
    packets_pool = rte_mempool_create(
        "packets",
        NUM_PKTS,
        MBUF_SIZE,
        CACHE_SIZE,                    //This is the size of the mempool
cache
        sizeof(struct rte_pktmbuf_pool_private),
        rte_pktmbuf_pool_init,
        NULL,
        rte_pktmbuf_init,
        NULL,
        rte_socket_id(),
        0 /*NO_FLAGS*/);

    if (packets_pool == NULL)
        rte_exit(EXIT_FAILURE,"Cannot init the packets pool\n");

    //Create metadata file
    if (rte_ivshmem_metadata_create(metadata_name) < 0)
        rte_exit(EXIT_FAILURE, "Cannot create metadata file\n");

    //Add mempool to metadata file
    if(rte_ivshmem_metadata_add_mempool(packets_pool, metadata_name) < 0)
        rte_exit(EXIT_FAILURE, "Cannot add mempool metadata file\n");

    //Get qemu command line
    if (rte_ivshmem_metadata_cmdline_generate(cmdline, sizeof(cmdline),
            metadata_name) < 0)
        rte_exit(EXIT_FAILURE, "Failed generating command line for qemu\n");

    RTE_LOG(INFO, APP, "Command line for qemu: %s\n", cmdline);
    save_ivshmem_cmdline_to_file(cmdline);

    //Avoids the application closes
    char x = getchar();
    (void) x;
    return 0;
}

When I run it I can see clearly that the memzone is added:

EAL: Adding memzone 'MP_packets' at 0x7ffec0e8c1c0 to metadata vm_1
EAL: Adding memzone 'RG_MP_packets' at 0x7ffec0d8c140 to metadata vm_1
APP: Command line for qemu: -device
ivshmem,size=2048M,shm=fd:/dev/hugepages/rtemap_0:0x0:0x40000000:/dev/zero:0x0:0x3fffc000:/var/run/.dpdk_ivshmem_metadata_vm_1:0x0:0x4000

I run the modified version of QEMU provided by dpdk-ovs using the command
line generated by the host application, then in the guest I run an even
simpler application:

...
void mempool_walk_f(const struct rte_mempool *r, void * arg)
{
    RTE_LOG(INFO, APP, "Mempool: %s\n", r->name);
    (void) arg;
}

int main(int argc, char *argv[])
{
    int retval = 0;

    if ((retval = rte_eal_init(argc, argv)) < 0)
        return -1;

    argc -= retval;
    argv += retval;

    struct rte_mempool * packets;

    packets = rte_mempool_lookup("packets");

    if(packets == NULL)
    {
        RTE_LOG(ERR, APP, "Failed to find mempool\n");
    }

    RTE_LOG(INFO, APP, "List of mempool: \n");
    rte_mempool_walk(mempool_walk_f, NULL);

    return 0;
}
...

I can see in the application output that the mem zones that were added are
found:

EAL: Found memzone: 'RG_MP_packets' at 0x7ffec0d8c140 (len 0x100080)
EAL: Found memzone: 'MP_packets' at 0x7ffec0e8c1c0 (len 0x3832100)

But, the rte_mempool_lookup function returns NULL.
Using the rte_mempool_walker the program only prints a memzone called
log_history.

Do you have any suggestion?

Thank you very much for your help.