kmod-redhat-mlx5_core/SOURCES/0006-netdrv-mlx5e-Allow-XSK-frames-smaller-than-a-page.patch

From d1ac1b641ea39e946e94c155520c590a5a27e23a Mon Sep 17 00:00:00 2001
From: Jiri Benc <jbenc@redhat.com>
Date: Wed, 22 Apr 2020 18:18:11 -0400
Subject: [PATCH 006/312] [netdrv] mlx5e: Allow XSK frames smaller than a page
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Message-id: <5c0604430537e1022e4424f8683b5611f3ccceb3.1587578778.git.jbenc@redhat.com>
Patchwork-id: 304531
Patchwork-instance: patchwork
O-Subject: [RHEL8.3 net 20/46] net/mlx5e: Allow XSK frames smaller than a page
Bugzilla: 1819630
RH-Acked-by: Hangbin Liu <haliu@redhat.com>
RH-Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
RH-Acked-by: Ivan Vecera <ivecera@redhat.com>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1819630

commit 282c0c798f8ec883c2ac2f1ce2dc06ef9421731c
Author: Maxim Mikityanskiy <maximmi@mellanox.com>
Date:   Tue Aug 27 02:25:26 2019 +0000

    net/mlx5e: Allow XSK frames smaller than a page

    Relax the requirements to the XSK frame size to allow it to be smaller
    than a page and even not a power of two. The current implementation can
    work in this mode, both with Striding RQ and without it.

    The code that checks `mtu + headroom <= XSK frame size` is modified
    accordingly. Any frame size between 2048 and PAGE_SIZE is accepted.

    Functions that worked with pages only now work with XSK frames, even if
    their size is different from PAGE_SIZE.

    With XSK queues, regardless of the frame size, Striding RQ uses the
    stride size of PAGE_SIZE, and UMR MTTs are posted using starting
    addresses of frames, but PAGE_SIZE as page size. MTU guarantees that no
    packet data will overlap with other frames. UMR MTT size is made equal
    to the stride size of the RQ, because UMEM frames may come in random
    order, and we need to handle them one by one. PAGE_SIZE is just a power
    of two that is bigger than any allowed XSK frame size, and also it
    doesn't require making additional changes to the code.

    Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
    Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
    Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Timothy Redaelli <tredaelli@redhat.com>
Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>
---
 .../net/ethernet/mellanox/mlx5/core/en/params.c    | 23 ++++++++++++++++++----
 .../net/ethernet/mellanox/mlx5/core/en/params.h    |  2 ++
 .../net/ethernet/mellanox/mlx5/core/en/xsk/rx.c    |  2 +-
 .../net/ethernet/mellanox/mlx5/core/en/xsk/setup.c | 15 +++++++++-----
 4 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
index 79301d116667..eb2e1f2138e4 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -25,18 +25,33 @@ u16 mlx5e_get_linear_rq_headroom(struct mlx5e_params *params,
 	return headroom;
 }
 
-u32 mlx5e_rx_get_linear_frag_sz(struct mlx5e_params *params,
-				struct mlx5e_xsk_param *xsk)
+u32 mlx5e_rx_get_min_frag_sz(struct mlx5e_params *params,
+			     struct mlx5e_xsk_param *xsk)
 {
 	u32 hw_mtu = MLX5E_SW2HW_MTU(params, params->sw_mtu);
 	u16 linear_rq_headroom = mlx5e_get_linear_rq_headroom(params, xsk);
-	u32 frag_sz = linear_rq_headroom + hw_mtu;
+
+	return linear_rq_headroom + hw_mtu;
+}
+
+u32 mlx5e_rx_get_linear_frag_sz(struct mlx5e_params *params,
+				struct mlx5e_xsk_param *xsk)
+{
+	u32 frag_sz = mlx5e_rx_get_min_frag_sz(params, xsk);
 
 	/* AF_XDP doesn't build SKBs in place. */
 	if (!xsk)
 		frag_sz = MLX5_SKB_FRAG_SZ(frag_sz);
 
-	/* XDP in mlx5e doesn't support multiple packets per page. */
+	/* XDP in mlx5e doesn't support multiple packets per page. AF_XDP is a
+	 * special case. It can run with frames smaller than a page, as it
+	 * doesn't allocate pages dynamically. However, here we pretend that
+	 * fragments are page-sized: it allows to treat XSK frames like pages
+	 * by redirecting alloc and free operations to XSK rings and by using
+	 * the fact there are no multiple packets per "page" (which is a frame).
+	 * The latter is important, because frames may come in a random order,
+	 * and we will have trouble assemblying a real page of multiple frames.
+	 */
 	if (mlx5e_rx_is_xdp(params, xsk))
 		frag_sz = max_t(u32, frag_sz, PAGE_SIZE);
 
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.h b/drivers/net/ethernet/mellanox/mlx5/core/en/params.h
index 3a615d663d84..989d8f429438 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.h
@@ -76,6 +76,8 @@ static inline bool mlx5e_qid_validate(const struct mlx5e_profile *profile,
 
 u16 mlx5e_get_linear_rq_headroom(struct mlx5e_params *params,
 				 struct mlx5e_xsk_param *xsk);
+u32 mlx5e_rx_get_min_frag_sz(struct mlx5e_params *params,
+			     struct mlx5e_xsk_param *xsk);
 u32 mlx5e_rx_get_linear_frag_sz(struct mlx5e_params *params,
 				struct mlx5e_xsk_param *xsk);
 u8 mlx5e_mpwqe_log_pkts_per_wqe(struct mlx5e_params *params,
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/rx.c
index 6a55573ec8f2..3783776b6d70 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/rx.c
@@ -104,7 +104,7 @@ struct sk_buff *mlx5e_xsk_skb_from_cqe_mpwrq_linear(struct mlx5e_rq *rq,
 
 	/* head_offset is not used in this function, because di->xsk.data and
 	 * di->addr point directly to the necessary place. Furthermore, in the
-	 * current implementation, one page = one packet = one frame, so
+	 * current implementation, UMR pages are mapped to XSK frames, so
 	 * head_offset should always be 0.
 	 */
 	WARN_ON_ONCE(head_offset);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
index d3a173e88e24..81efd2fbc75d 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
@@ -4,18 +4,23 @@
 #include "setup.h"
 #include "en/params.h"
 
+/* It matches XDP_UMEM_MIN_CHUNK_SIZE, but as this constant is private and may
+ * change unexpectedly, and mlx5e has a minimum valid stride size for striding
+ * RQ, keep this check in the driver.
+ */
+#define MLX5E_MIN_XSK_CHUNK_SIZE 2048
+
 bool mlx5e_validate_xsk_param(struct mlx5e_params *params,
 			      struct mlx5e_xsk_param *xsk,
 			      struct mlx5_core_dev *mdev)
 {
-	/* AF_XDP doesn't support frames larger than PAGE_SIZE, and the current
-	 * mlx5e XDP implementation doesn't support multiple packets per page.
-	 */
-	if (xsk->chunk_size != PAGE_SIZE)
+	/* AF_XDP doesn't support frames larger than PAGE_SIZE. */
+	if (xsk->chunk_size > PAGE_SIZE ||
+			xsk->chunk_size < MLX5E_MIN_XSK_CHUNK_SIZE)
 		return false;
 
 	/* Current MTU and XSK headroom don't allow packets to fit the frames. */
-	if (mlx5e_rx_get_linear_frag_sz(params, xsk) > xsk->chunk_size)
+	if (mlx5e_rx_get_min_frag_sz(params, xsk) > xsk->chunk_size)
 		return false;
 
 	/* frag_sz is different for regular and XSK RQs, so ensure that linear
-- 
2.13.6