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Message-ID: <CAHS8izN-PXYC0GspMFPqeACqDTTRK_B8guuXc6+KAXRFaSPG6Q@mail.gmail.com>
Date: Fri, 1 Nov 2024 07:53:15 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Taehee Yoo <ap420073@...il.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
edumazet@...gle.com, donald.hunter@...il.com, corbet@....net,
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maxime.chevallier@...tlin.com, danieller@...dia.com, hengqi@...ux.alibaba.com,
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willemb@...gle.com, daniel.zahka@...il.com
Subject: Re: [PATCH net-next v4 8/8] bnxt_en: add support for device memory tcp
On Tue, Oct 22, 2024 at 9:25 AM Taehee Yoo <ap420073@...il.com> wrote:
>
> Currently, bnxt_en driver satisfies the requirements of Device memory
> TCP, which is tcp-data-split.
> So, it implements Device memory TCP for bnxt_en driver.
>
> From now on, the aggregation ring handles netmem_ref instead of page
> regardless of the on/off of netmem.
> So, for the aggregation ring, memory will be handled with the netmem
> page_pool API instead of generic page_pool API.
>
> If Devmem is enabled, netmem_ref is used as-is and if Devmem is not
> enabled, netmem_ref will be converted to page and that is used.
>
> Driver recognizes whether the devmem is set or unset based on the
> mp_params.mp_priv is not NULL.
> Only if devmem is set, it passes PP_FLAG_ALLOW_UNREADABLE_NETMEM.
Looks like in the latest version, you pass
PP_FLAG_ALLOW_UNREADABLE_NETMEM unconditionally, so this line is
obsolete.
However, I think you should only pass PP_FLAG_ALLOW_UNREADABLE_NETMEM
if hds_thresh==0 and tcp-data-split==1, because otherwise the driver
is not configured well enough to handle unreadable netmem, right? I
know that we added checks in the devmem binding to detect hds_thresh
and tcp-data-split, but we should keep another layer of protection in
the driver. The driver should not set PP_FLAG_ALLOW_UNREADABLE_NETMEM
unless it's configured to be able to handle unreadable netmem.
>
> Tested-by: Stanislav Fomichev <sdf@...ichev.me>
> Signed-off-by: Taehee Yoo <ap420073@...il.com>
> ---
>
> v4:
> - Do not select NET_DEVMEM in Kconfig.
> - Pass PP_FLAG_ALLOW_UNREADABLE_NETMEM flag unconditionally.
> - Add __bnxt_rx_agg_pages_xdp().
> - Use gfp flag in __bnxt_alloc_rx_netmem().
> - Do not add *offset in the __bnxt_alloc_rx_netmem().
> - Do not pass queue_idx to bnxt_alloc_rx_page_pool().
> - Add Test tag from Stanislav.
> - Add page_pool_recycle_direct_netmem() helper.
>
> v3:
> - Patch added.
>
> drivers/net/ethernet/broadcom/bnxt/bnxt.c | 182 ++++++++++++++++------
> drivers/net/ethernet/broadcom/bnxt/bnxt.h | 2 +-
> include/net/page_pool/helpers.h | 6 +
> 3 files changed, 142 insertions(+), 48 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 7d9da483b867..7924b1da0413 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -55,6 +55,7 @@
> #include <net/page_pool/helpers.h>
> #include <linux/align.h>
> #include <net/netdev_queues.h>
> +#include <net/netdev_rx_queue.h>
>
> #include "bnxt_hsi.h"
> #include "bnxt.h"
> @@ -863,6 +864,22 @@ static void bnxt_tx_int(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
> bnapi->events &= ~BNXT_TX_CMP_EVENT;
> }
>
> +static netmem_ref __bnxt_alloc_rx_netmem(struct bnxt *bp, dma_addr_t *mapping,
> + struct bnxt_rx_ring_info *rxr,
> + unsigned int *offset,
> + gfp_t gfp)
> +{
> + netmem_ref netmem;
> +
> + netmem = page_pool_alloc_netmem(rxr->page_pool, gfp);
> + if (!netmem)
> + return 0;
> + *offset = 0;
> +
> + *mapping = page_pool_get_dma_addr_netmem(netmem);
> + return netmem;
> +}
> +
> static struct page *__bnxt_alloc_rx_page(struct bnxt *bp, dma_addr_t *mapping,
> struct bnxt_rx_ring_info *rxr,
> unsigned int *offset,
> @@ -972,21 +989,21 @@ static inline u16 bnxt_find_next_agg_idx(struct bnxt_rx_ring_info *rxr, u16 idx)
> return next;
> }
>
> -static inline int bnxt_alloc_rx_page(struct bnxt *bp,
> - struct bnxt_rx_ring_info *rxr,
> - u16 prod, gfp_t gfp)
> +static inline int bnxt_alloc_rx_netmem(struct bnxt *bp,
> + struct bnxt_rx_ring_info *rxr,
> + u16 prod, gfp_t gfp)
> {
> struct rx_bd *rxbd =
> &rxr->rx_agg_desc_ring[RX_AGG_RING(bp, prod)][RX_IDX(prod)];
> struct bnxt_sw_rx_agg_bd *rx_agg_buf;
> - struct page *page;
> - dma_addr_t mapping;
> u16 sw_prod = rxr->rx_sw_agg_prod;
> unsigned int offset = 0;
> + dma_addr_t mapping;
> + netmem_ref netmem;
>
> - page = __bnxt_alloc_rx_page(bp, &mapping, rxr, &offset, gfp);
> + netmem = __bnxt_alloc_rx_netmem(bp, &mapping, rxr, &offset, gfp);
>
> - if (!page)
> + if (!netmem)
> return -ENOMEM;
>
> if (unlikely(test_bit(sw_prod, rxr->rx_agg_bmap)))
> @@ -996,7 +1013,7 @@ static inline int bnxt_alloc_rx_page(struct bnxt *bp,
> rx_agg_buf = &rxr->rx_agg_ring[sw_prod];
> rxr->rx_sw_agg_prod = RING_RX_AGG(bp, NEXT_RX_AGG(sw_prod));
>
> - rx_agg_buf->page = page;
> + rx_agg_buf->netmem = netmem;
> rx_agg_buf->offset = offset;
> rx_agg_buf->mapping = mapping;
> rxbd->rx_bd_haddr = cpu_to_le64(mapping);
> @@ -1044,7 +1061,7 @@ static void bnxt_reuse_rx_agg_bufs(struct bnxt_cp_ring_info *cpr, u16 idx,
> struct rx_agg_cmp *agg;
> struct bnxt_sw_rx_agg_bd *cons_rx_buf, *prod_rx_buf;
> struct rx_bd *prod_bd;
> - struct page *page;
> + netmem_ref netmem;
>
> if (p5_tpa)
> agg = bnxt_get_tpa_agg_p5(bp, rxr, idx, start + i);
> @@ -1061,11 +1078,11 @@ static void bnxt_reuse_rx_agg_bufs(struct bnxt_cp_ring_info *cpr, u16 idx,
> cons_rx_buf = &rxr->rx_agg_ring[cons];
>
> /* It is possible for sw_prod to be equal to cons, so
> - * set cons_rx_buf->page to NULL first.
> + * set cons_rx_buf->netmem to 0 first.
> */
> - page = cons_rx_buf->page;
> - cons_rx_buf->page = NULL;
> - prod_rx_buf->page = page;
> + netmem = cons_rx_buf->netmem;
> + cons_rx_buf->netmem = 0;
> + prod_rx_buf->netmem = netmem;
> prod_rx_buf->offset = cons_rx_buf->offset;
>
> prod_rx_buf->mapping = cons_rx_buf->mapping;
> @@ -1190,29 +1207,104 @@ static struct sk_buff *bnxt_rx_skb(struct bnxt *bp,
> return skb;
> }
>
> -static u32 __bnxt_rx_agg_pages(struct bnxt *bp,
> - struct bnxt_cp_ring_info *cpr,
> - struct skb_shared_info *shinfo,
> - u16 idx, u32 agg_bufs, bool tpa,
> - struct xdp_buff *xdp)
> +static bool __bnxt_rx_agg_pages_skb(struct bnxt *bp,
> + struct bnxt_cp_ring_info *cpr,
> + struct sk_buff *skb,
> + u16 idx, u32 agg_bufs, bool tpa)
> {
To be honest I could not immediately understand why
__bnxt_rx_agg_pages needed to be split into __bnxt_rx_agg_pages_skb
and __bnxt_rx_agg_pages_xdp.
Fundamentally speaking we wanted the netmem transition to be as smooth
and low-churn as possible for drivers. The only big changes in this
patch are the split between skb and xdp. That points to a problem in
the design of netmem maybe.
For xdp, core makes sure that if xdp is enabled on the device, then
the netmem is always pages (never unreadable). So I think netmem
should be able to handle xdp as well as skb. Can you give more details
on why the split?
> struct bnxt_napi *bnapi = cpr->bnapi;
> struct pci_dev *pdev = bp->pdev;
> - struct bnxt_rx_ring_info *rxr = bnapi->rx_ring;
> - u16 prod = rxr->rx_agg_prod;
> + struct bnxt_rx_ring_info *rxr;
> u32 i, total_frag_len = 0;
> bool p5_tpa = false;
> + u16 prod;
> +
> + rxr = bnapi->rx_ring;
> + prod = rxr->rx_agg_prod;
>
> if ((bp->flags & BNXT_FLAG_CHIP_P5_PLUS) && tpa)
> p5_tpa = true;
>
> for (i = 0; i < agg_bufs; i++) {
> - skb_frag_t *frag = &shinfo->frags[i];
> - u16 cons, frag_len;
> + struct bnxt_sw_rx_agg_bd *cons_rx_buf;
> struct rx_agg_cmp *agg;
> + u16 cons, frag_len;
> + dma_addr_t mapping;
> + netmem_ref netmem;
> +
> + if (p5_tpa)
> + agg = bnxt_get_tpa_agg_p5(bp, rxr, idx, i);
> + else
> + agg = bnxt_get_agg(bp, cpr, idx, i);
> + cons = agg->rx_agg_cmp_opaque;
> + frag_len = (le32_to_cpu(agg->rx_agg_cmp_len_flags_type) &
> + RX_AGG_CMP_LEN) >> RX_AGG_CMP_LEN_SHIFT;
> +
> + cons_rx_buf = &rxr->rx_agg_ring[cons];
> + skb_add_rx_frag_netmem(skb, i, cons_rx_buf->netmem,
> + cons_rx_buf->offset, frag_len,
> + BNXT_RX_PAGE_SIZE);
> + __clear_bit(cons, rxr->rx_agg_bmap);
> +
> + /* It is possible for bnxt_alloc_rx_netmem() to allocate
> + * a sw_prod index that equals the cons index, so we
> + * need to clear the cons entry now.
> + */
> + mapping = cons_rx_buf->mapping;
> + netmem = cons_rx_buf->netmem;
> + cons_rx_buf->netmem = 0;
> +
> + if (bnxt_alloc_rx_netmem(bp, rxr, prod, GFP_ATOMIC) != 0) {
> + skb->len -= frag_len;
> + skb->data_len -= frag_len;
> + skb->truesize -= BNXT_RX_PAGE_SIZE;
> + --skb_shinfo(skb)->nr_frags;
> + cons_rx_buf->netmem = netmem;
> +
> + /* Update prod since possibly some pages have been
> + * allocated already.
> + */
> + rxr->rx_agg_prod = prod;
> + bnxt_reuse_rx_agg_bufs(cpr, idx, i, agg_bufs - i, tpa);
> + return 0;
> + }
> +
> + dma_sync_single_for_cpu(&pdev->dev, mapping, BNXT_RX_PAGE_SIZE,
> + bp->rx_dir);
> +
You should probably use page_pool_dma_sync_for_cpu. I'm merging a
change to make that function skip dma-syncing for net_iov:
https://lore.kernel.org/netdev/20241029204541.1301203-5-almasrymina@google.com/
Which is necessary following Jason Gunthorpe's guidance.
> + total_frag_len += frag_len;
> + prod = NEXT_RX_AGG(prod);
> + }
> + rxr->rx_agg_prod = prod;
> + return total_frag_len;
> +}
> +
> +static u32 __bnxt_rx_agg_pages_xdp(struct bnxt *bp,
> + struct bnxt_cp_ring_info *cpr,
> + struct skb_shared_info *shinfo,
> + u16 idx, u32 agg_bufs, bool tpa,
> + struct xdp_buff *xdp)
> +{
> + struct bnxt_napi *bnapi = cpr->bnapi;
> + struct pci_dev *pdev = bp->pdev;
> + struct bnxt_rx_ring_info *rxr;
> + u32 i, total_frag_len = 0;
> + bool p5_tpa = false;
> + u16 prod;
> +
> + rxr = bnapi->rx_ring;
> + prod = rxr->rx_agg_prod;
> +
> + if ((bp->flags & BNXT_FLAG_CHIP_P5_PLUS) && tpa)
> + p5_tpa = true;
> +
> + for (i = 0; i < agg_bufs; i++) {
> struct bnxt_sw_rx_agg_bd *cons_rx_buf;
> - struct page *page;
> + skb_frag_t *frag = &shinfo->frags[i];
> + struct rx_agg_cmp *agg;
> + u16 cons, frag_len;
> dma_addr_t mapping;
> + netmem_ref netmem;
>
> if (p5_tpa)
> agg = bnxt_get_tpa_agg_p5(bp, rxr, idx, i);
> @@ -1223,9 +1315,10 @@ static u32 __bnxt_rx_agg_pages(struct bnxt *bp,
> RX_AGG_CMP_LEN) >> RX_AGG_CMP_LEN_SHIFT;
>
> cons_rx_buf = &rxr->rx_agg_ring[cons];
> - skb_frag_fill_page_desc(frag, cons_rx_buf->page,
> - cons_rx_buf->offset, frag_len);
> + skb_frag_fill_netmem_desc(frag, cons_rx_buf->netmem,
> + cons_rx_buf->offset, frag_len);
> shinfo->nr_frags = i + 1;
> +
> __clear_bit(cons, rxr->rx_agg_bmap);
>
> /* It is possible for bnxt_alloc_rx_page() to allocate
> @@ -1233,15 +1326,15 @@ static u32 __bnxt_rx_agg_pages(struct bnxt *bp,
> * need to clear the cons entry now.
> */
> mapping = cons_rx_buf->mapping;
> - page = cons_rx_buf->page;
> - cons_rx_buf->page = NULL;
> + netmem = cons_rx_buf->netmem;
> + cons_rx_buf->netmem = 0;
>
> - if (xdp && page_is_pfmemalloc(page))
> + if (netmem_is_pfmemalloc(netmem))
> xdp_buff_set_frag_pfmemalloc(xdp);
>
> - if (bnxt_alloc_rx_page(bp, rxr, prod, GFP_ATOMIC) != 0) {
> + if (bnxt_alloc_rx_netmem(bp, rxr, prod, GFP_ATOMIC) != 0) {
> --shinfo->nr_frags;
> - cons_rx_buf->page = page;
> + cons_rx_buf->netmem = netmem;
>
> /* Update prod since possibly some pages have been
> * allocated already.
> @@ -1266,20 +1359,12 @@ static struct sk_buff *bnxt_rx_agg_pages_skb(struct bnxt *bp,
> struct sk_buff *skb, u16 idx,
> u32 agg_bufs, bool tpa)
> {
> - struct skb_shared_info *shinfo = skb_shinfo(skb);
> - u32 total_frag_len = 0;
> -
> - total_frag_len = __bnxt_rx_agg_pages(bp, cpr, shinfo, idx,
> - agg_bufs, tpa, NULL);
> - if (!total_frag_len) {
> + if (!__bnxt_rx_agg_pages_skb(bp, cpr, skb, idx, agg_bufs, tpa)) {
> skb_mark_for_recycle(skb);
> dev_kfree_skb(skb);
> return NULL;
> }
>
> - skb->data_len += total_frag_len;
> - skb->len += total_frag_len;
> - skb->truesize += BNXT_RX_PAGE_SIZE * agg_bufs;
> return skb;
> }
>
> @@ -1294,8 +1379,8 @@ static u32 bnxt_rx_agg_pages_xdp(struct bnxt *bp,
> if (!xdp_buff_has_frags(xdp))
> shinfo->nr_frags = 0;
>
> - total_frag_len = __bnxt_rx_agg_pages(bp, cpr, shinfo,
> - idx, agg_bufs, tpa, xdp);
> + total_frag_len = __bnxt_rx_agg_pages_xdp(bp, cpr, shinfo,
> + idx, agg_bufs, tpa, xdp);
> if (total_frag_len) {
> xdp_buff_set_frags_flag(xdp);
> shinfo->nr_frags = agg_bufs;
> @@ -3341,15 +3426,15 @@ static void bnxt_free_one_rx_agg_ring(struct bnxt *bp, struct bnxt_rx_ring_info
>
> for (i = 0; i < max_idx; i++) {
> struct bnxt_sw_rx_agg_bd *rx_agg_buf = &rxr->rx_agg_ring[i];
> - struct page *page = rx_agg_buf->page;
> + netmem_ref netmem = rx_agg_buf->netmem;
>
> - if (!page)
> + if (!netmem)
> continue;
>
> - rx_agg_buf->page = NULL;
> + rx_agg_buf->netmem = 0;
> __clear_bit(i, rxr->rx_agg_bmap);
>
> - page_pool_recycle_direct(rxr->page_pool, page);
> + page_pool_recycle_direct_netmem(rxr->page_pool, netmem);
> }
> }
>
> @@ -3620,7 +3705,10 @@ static int bnxt_alloc_rx_page_pool(struct bnxt *bp,
> pp.dev = &bp->pdev->dev;
> pp.dma_dir = bp->rx_dir;
> pp.max_len = PAGE_SIZE;
> - pp.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV;
> + pp.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV |
> + PP_FLAG_ALLOW_UNREADABLE_NETMEM;
PP_FLAG_ALLOW_UNREADABLE_NETMEM should only be set when the driver can
handle unreadable netmem. I.e. when hds_thresh==0 and
tcp-data-split==1.
--
Thanks,
Mina
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