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Date: Sun, 6 Oct 2019 00:34:52 +0300
From: Ilias Apalodimas <ilias.apalodimas@...aro.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net,
thomas.petazzoni@...tlin.com, brouer@...hat.com,
lorenzo.bianconi@...hat.com, matteo.croce@...hat.com
Subject: Re: [PATCH 2/7] net: mvneta: introduce page pool API for sw buffer
manager
Hi Lorenzo,
On Sat, Oct 05, 2019 at 10:44:35PM +0200, Lorenzo Bianconi wrote:
> Use the page_pool api for allocations and DMA handling instead of
> __dev_alloc_page()/dma_map_page() and free_page()/dma_unmap_page().
> Pages are unmapped using page_pool_release_page before packets
> go into the network stack.
>
> The page_pool API offers buffer recycling capabilities for XDP but
> allocates one page per packet, unless the driver splits and manages
> the allocated page.
> This is a preliminary patch to add XDP support to mvneta driver
>
> Tested-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
> drivers/net/ethernet/marvell/Kconfig | 1 +
> drivers/net/ethernet/marvell/mvneta.c | 76 ++++++++++++++++++++-------
> 2 files changed, 58 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/Kconfig b/drivers/net/ethernet/marvell/Kconfig
> index fb942167ee54..3d5caea096fb 100644
> --- a/drivers/net/ethernet/marvell/Kconfig
> +++ b/drivers/net/ethernet/marvell/Kconfig
> @@ -61,6 +61,7 @@ config MVNETA
> depends on ARCH_MVEBU || COMPILE_TEST
> select MVMDIO
> select PHYLINK
> + select PAGE_POOL
> ---help---
> This driver supports the network interface units in the
> Marvell ARMADA XP, ARMADA 370, ARMADA 38x and
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 128b9fded959..8beae0e1eda7 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -37,6 +37,7 @@
> #include <net/ip.h>
> #include <net/ipv6.h>
> #include <net/tso.h>
> +#include <net/page_pool.h>
>
> /* Registers */
> #define MVNETA_RXQ_CONFIG_REG(q) (0x1400 + ((q) << 2))
> @@ -603,6 +604,10 @@ struct mvneta_rx_queue {
> u32 pkts_coal;
> u32 time_coal;
>
> + /* page_pool */
> + struct page_pool *page_pool;
> + struct xdp_rxq_info xdp_rxq;
> +
> /* Virtual address of the RX buffer */
> void **buf_virt_addr;
>
> @@ -1815,19 +1820,12 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
> dma_addr_t phys_addr;
> struct page *page;
>
> - page = __dev_alloc_page(gfp_mask);
> + page = page_pool_alloc_pages(rxq->page_pool,
> + gfp_mask | __GFP_NOWARN);
> if (!page)
> return -ENOMEM;
Is the driver syncing the buffer somewhere else? (for_device)
If not you'll have to do this here.
On a non-cache coherent machine (and i think this one is) you may get dirty
cache lines handed to the device. Those dirty cache lines might get written back
*after* the device has DMA'ed it's data. You need to flush those first to avoid
any data corruption
>
> - /* map page for use */
> - phys_addr = dma_map_page(pp->dev->dev.parent, page, 0, PAGE_SIZE,
> - DMA_FROM_DEVICE);
> - if (unlikely(dma_mapping_error(pp->dev->dev.parent, phys_addr))) {
> - __free_page(page);
> - return -ENOMEM;
> - }
> -
> - phys_addr += pp->rx_offset_correction;
> + phys_addr = page_pool_get_dma_addr(page) + pp->rx_offset_correction;
> mvneta_rx_desc_fill(rx_desc, phys_addr, page, rxq);
> return 0;
> }
> @@ -1894,10 +1892,11 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
> if (!data || !(rx_desc->buf_phys_addr))
> continue;
>
> - dma_unmap_page(pp->dev->dev.parent, rx_desc->buf_phys_addr,
> - PAGE_SIZE, DMA_FROM_DEVICE);
> - __free_page(data);
> + page_pool_put_page(rxq->page_pool, data, false);
> }
> + if (xdp_rxq_info_is_reg(&rxq->xdp_rxq))
> + xdp_rxq_info_unreg(&rxq->xdp_rxq);
> + page_pool_destroy(rxq->page_pool);
> }
>
> static void
> @@ -2029,8 +2028,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
> skb_add_rx_frag(rxq->skb, frag_num, page,
> frag_offset, frag_size,
> PAGE_SIZE);
> - dma_unmap_page(dev->dev.parent, phys_addr,
> - PAGE_SIZE, DMA_FROM_DEVICE);
> + page_pool_release_page(rxq->page_pool, page);
> rxq->left_size -= frag_size;
> }
> } else {
> @@ -2060,9 +2058,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
> frag_offset, frag_size,
> PAGE_SIZE);
>
> - dma_unmap_page(dev->dev.parent, phys_addr,
> - PAGE_SIZE, DMA_FROM_DEVICE);
> -
> + page_pool_release_page(rxq->page_pool, page);
> rxq->left_size -= frag_size;
> }
> } /* Middle or Last descriptor */
> @@ -2829,11 +2825,53 @@ static int mvneta_poll(struct napi_struct *napi, int budget)
> return rx_done;
> }
>
> +static int mvneta_create_page_pool(struct mvneta_port *pp,
> + struct mvneta_rx_queue *rxq, int size)
> +{
> + struct page_pool_params pp_params = {
> + .order = 0,
> + .flags = PP_FLAG_DMA_MAP,
> + .pool_size = size,
> + .nid = cpu_to_node(0),
> + .dev = pp->dev->dev.parent,
> + .dma_dir = DMA_FROM_DEVICE,
> + };
> + int err;
> +
> + rxq->page_pool = page_pool_create(&pp_params);
> + if (IS_ERR(rxq->page_pool)) {
> + err = PTR_ERR(rxq->page_pool);
> + rxq->page_pool = NULL;
> + return err;
> + }
> +
> + err = xdp_rxq_info_reg(&rxq->xdp_rxq, pp->dev, 0);
> + if (err < 0)
> + goto err_free_pp;
> +
> + err = xdp_rxq_info_reg_mem_model(&rxq->xdp_rxq, MEM_TYPE_PAGE_POOL,
> + rxq->page_pool);
> + if (err)
> + goto err_unregister_rxq;
> +
> + return 0;
> +
> +err_unregister_rxq:
> + xdp_rxq_info_unreg(&rxq->xdp_rxq);
> +err_free_pp:
> + page_pool_destroy(rxq->page_pool);
> + return err;
> +}
> +
> /* Handle rxq fill: allocates rxq skbs; called when initializing a port */
> static int mvneta_rxq_fill(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> int num)
> {
> - int i;
> + int i, err;
> +
> + err = mvneta_create_page_pool(pp, rxq, num);
> + if (err < 0)
> + return err;
>
> for (i = 0; i < num; i++) {
> memset(rxq->descs + i, 0, sizeof(struct mvneta_rx_desc));
> --
> 2.21.0
>
Thanks
/Ilias
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