Re: [dpdk-dev] [PATCH] ethdev: add size and align to compose dma zone name strings

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 4/29/19 11:03 AM, David Marchand wrote:
> On Sat, Apr 27, 2019 at 11:48 AM wangyunjian <wangyunjian@huawei.com 
> <mailto:wangyunjian@huawei.com>> wrote:
>
>     From: Yunjian Wang <wangyunjian@huawei.com
>     <mailto:wangyunjian@huawei.com>>
>
>     The current dma zone name consists of the port_id, queue_id and
>     ring_name. If a port_id is reused, a new nic maybe use same dma
>     zone name. At this time, the zone size of the new driver is
>     differnt. When the zone is reused, it may cause illegal access
>     to memory.
>
>     Signed-off-by: Yunjian Wang <wangyunjian@huawei.com
>     <mailto:wangyunjian@huawei.com>>
>     ---
>      lib/librte_ethdev/rte_ethdev.c | 6 +++---
>      1 file changed, 3 insertions(+), 3 deletions(-)
>
>     diff --git a/lib/librte_ethdev/rte_ethdev.c
>     b/lib/librte_ethdev/rte_ethdev.c
>     index d7cfa3d..0703cda 100644
>     --- a/lib/librte_ethdev/rte_ethdev.c
>     +++ b/lib/librte_ethdev/rte_ethdev.c
>     @@ -3630,9 +3630,9 @@ int rte_eth_set_queue_rate_limit(uint16_t
>     port_id, uint16_t queue_idx,
>             const struct rte_memzone *mz;
>             int rc;
>
>     -       rc = snprintf(z_name, sizeof(z_name), "eth_p%d_q%d_%s",
>     -                     dev->data->port_id, queue_id, ring_name);
>     -       if (rc >= RTE_MEMZONE_NAMESIZE) {
>     +       rc = snprintf(z_name, sizeof(z_name), "p%dq%d%s0x%zx_%d",
>     +                     dev->data->port_id, queue_id, ring_name,
>     size, align);
>     +       if (rc >= RTE_MEMZONE_NAMESIZE || rc < 0) {
>                     RTE_ETHDEV_LOG(ERR, "ring name too long\n");
>                     rte_errno = ENAMETOOLONG;
>                     return NULL;
>
>
> In such a case, we are leaving the previous memzone in place and just 
> creating a new one.
> Should the driver free the previous memzone instead?
>
> I can't see this in existing drivers.
> Do we actually expect to reuse the existing memzones?
>

I don't think the patch is a right way to go.
It is related to [1] which has a long discussion.

Andrew.

[1] https://patches.dpdk.org/patch/51952/