[dpdk-dev] [dpdk-stable] [PATCH] net/af_xdp: fix 32-bit build for older kernels
Ferruh Yigit
ferruh.yigit at intel.com
Fri Nov 13 14:00:12 CET 2020
On 11/12/2020 4:35 PM, Ciara Loftus wrote:
> 'uint64_t' is used to hold pointers in multiple locations in the
> copy-mode code (used for kernels before 5.4). For a 32-bit build
> this assumption is wrong and results in build errors. This commit
> replaces such instances of 'uint64_t' with 'uintptr_t'.
>
> While the copy-mode code will now compile for 32-bit, the PMD is
> not expected to work and will fail at initialisation due to some
> limitations in the kernel that were subsequently removed in v5.4.
> Add a note to the docs to flag this limitation.
>
> Fixes: f1debd77efaf ("net/af_xdp: introduce AF_XDP PMD")
> Fixes: d8a210774e1d ("net/af_xdp: support unaligned umem chunks")
> Cc: stable at dpdk.org
>
> Signed-off-by: Ciara Loftus <ciara.loftus at intel.com>
> ---
> doc/guides/nics/af_xdp.rst | 1 +
> drivers/net/af_xdp/rte_eth_af_xdp.c | 6 +++---
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/doc/guides/nics/af_xdp.rst b/doc/guides/nics/af_xdp.rst
> index 052e59a3ae..5ed24374f8 100644
> --- a/doc/guides/nics/af_xdp.rst
> +++ b/doc/guides/nics/af_xdp.rst
> @@ -50,6 +50,7 @@ This is a Linux-specific PMD, thus the following prerequisites apply:
> * For PMD zero copy, it requires kernel version later than v5.4-rc1;
> * For shared_umem, it requires kernel version v5.10 or later and libbpf version
> v0.2.0 or later.
> +* For 32-bit OS, a kernel with version 5.4 or later is required.
>
+1 to doc update
> Set up an af_xdp interface
> -----------------------------
> diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
> index 4076ff797c..75ff1c00b2 100644
> --- a/drivers/net/af_xdp/rte_eth_af_xdp.c
> +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
> @@ -349,7 +349,7 @@ af_xdp_rx_cp(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>
> for (i = 0; i < rcvd; i++) {
> const struct xdp_desc *desc;
> - uint64_t addr;
> + uintptr_t addr;
> uint32_t len;
> void *pkt;
>
> @@ -402,7 +402,7 @@ pull_umem_cq(struct xsk_umem_info *umem, int size, struct xsk_ring_cons *cq)
> n = xsk_ring_cons__peek(cq, size, &idx_cq);
>
> for (i = 0; i < n; i++) {
> - uint64_t addr;
> + uintptr_t addr;
> addr = *xsk_ring_cons__comp_addr(cq, idx_cq++);
Hi Ciara,
As far as I can see the API 'xsk_ring_cons__comp_addr()' returns fixed size
variable ('__u64'),
and when the PMD is compiled for 32bit, won't it be assigning a 64bit variable
to the 32bit storage.
I guess libbpf also needs to be adjusted for the 32bit support, what about
making PMD changes after libbpf changed?
> #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG)
> addr = xsk_umem__extract_addr(addr);
> @@ -1005,7 +1005,7 @@ xsk_umem_info *xdp_umem_configure(struct pmd_internals *internals,
> char ring_name[RTE_RING_NAMESIZE];
> char mz_name[RTE_MEMZONE_NAMESIZE];
> int ret;
> - uint64_t i;
> + uintptr_t i;
>
Not sure on this one, 'i' seems not to hold a pointer but index, and result of
calculation cast to "void *", I assume intention is to prevent calculation
result to be 64 bit to cover the case "void *" is 4 bytes, for that what do you
think making variable uint32_t?
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