On Tue, Jul 11, 2023 at 01:47:04PM +0200, Sriram Yagnaraman wrote:
> Add support for AF_XDP zero-copy receive path.
>
> When AF_XDP zero-copy is enabled, the rx buffers are allocated from the
> xsk buff pool using igb_alloc_rx_buffers_zc.
>
> Use xsk_pool_get_rx_frame_size to set SRRCTL rx buf size when zero-copy
> is enabled.
>
> Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@xxxxxxxx>
Hi Sriram,
> +bool igb_alloc_rx_buffers_zc(struct igb_ring *rx_ring, u16 count)
> +{
> + union e1000_adv_rx_desc *rx_desc;
> + u32 nb_buffs_extra = 0, nb_buffs;
> + u16 ntu = rx_ring->next_to_use;
> + u16 total_count = count;
> + struct xdp_buff **xdp;
> +
> + rx_desc = IGB_RX_DESC(rx_ring, ntu);
> + xdp = &rx_ring->rx_buffer_info_zc[ntu];
> +
> + if (ntu + count >= rx_ring->count) {
> + nb_buffs_extra = igb_fill_rx_descs(rx_ring->xsk_pool, xdp,
> + rx_desc,
> + rx_ring->count - ntu);
> + if (nb_buffs_extra != rx_ring->count - ntu) {
> + ntu += nb_buffs_extra;
> + goto exit;
nb_buffs is uninitialised here...
> + }
> + rx_desc = IGB_RX_DESC(rx_ring, 0);
> + xdp = rx_ring->rx_buffer_info_zc;
> + ntu = 0;
> + count -= nb_buffs_extra;
> + }
> +
> + nb_buffs = igb_fill_rx_descs(rx_ring->xsk_pool, xdp, rx_desc, count);
> + ntu += nb_buffs;
> + if (ntu == rx_ring->count)
> + ntu = 0;
> +
> + /* clear the length for the next_to_use descriptor */
> + rx_desc = IGB_RX_DESC(rx_ring, ntu);
> + rx_desc->wb.upper.length = 0;
> +
> +exit:
> + if (rx_ring->next_to_use != ntu) {
> + rx_ring->next_to_use = ntu;
> +
> + /* Force memory writes to complete before letting h/w
> + * know there are new descriptors to fetch. (Only
> + * applicable for weak-ordered memory model archs,
> + * such as IA-64).
> + */
> + wmb();
> + writel(ntu, rx_ring->tail);
> + }
> +
> + return total_count == (nb_buffs + nb_buffs_extra);
But it is used here.
...
The following will tell you about this problem:
- Smatch
- clang-16 W=1 build [-Wsometimes-uninitialized]
- gcc-12 build with -Wmaybe-uninitialized
