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Message-ID: <20251129160405.2568284-15-den@valinux.co.jp>
Date: Sun, 30 Nov 2025 01:03:52 +0900
From: Koichiro Den <den@...inux.co.jp>
To: ntb@...ts.linux.dev,
linux-pci@...r.kernel.org,
dmaengine@...r.kernel.org,
linux-kernel@...r.kernel.org,
Frank.Li@....com
Cc: mani@...nel.org,
kwilczynski@...nel.org,
kishon@...nel.org,
bhelgaas@...gle.com,
corbet@....net,
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Subject: [RFC PATCH v2 14/27] NTB: ntb_transport: Move TX memory window setup into setup_qp_mw()
Historically both TX and RX have assumed the same per-QP MW slice
(tx_max_entry == remote rx_max_entry), while those are calculated
separately in different places (pre and post the link-up negotiation
point). This has been safe because nt->link_is_up is never set to true
unless the pre-determined qp_count are the same among them, and qp_count
is typically limited to nt->mw_count, which should be carefully
configured by admin.
However, setup_qp_mw can actually split mw and handle multi-qps in one
MW properly, so qp_count needs not to be limited by nt->mw_count. Once
we relaxing the limitation, pre-determined qp_count can differ among
host side and endpoint, and link-up negotiation can easily fail.
Move the TX MW configuration (per-QP offset and size) into
ntb_transport_setup_qp_mw() so that both RX and TX layout decisions are
centralized in a single helper. ntb_transport_init_queue() now deals
only with per-QP software state, not with MW layout.
This keeps the previous behaviour, while preparing for relaxing the
qp_count limitation and improving readibility.
No functional change is intended.
Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
drivers/ntb/ntb_transport.c | 67 ++++++++++++++-----------------------
1 file changed, 26 insertions(+), 41 deletions(-)
diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index 57b4c0511927..79063e2f911b 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -569,7 +569,8 @@ static int ntb_transport_setup_qp_mw(struct ntb_transport_ctx *nt,
struct ntb_transport_mw *mw;
struct ntb_dev *ndev = nt->ndev;
struct ntb_queue_entry *entry;
- unsigned int rx_size, num_qps_mw;
+ unsigned int num_qps_mw;
+ unsigned int mw_size, mw_size_per_qp, qp_offset, rx_info_offset;
unsigned int mw_num, mw_count, qp_count;
unsigned int i;
int node;
@@ -588,15 +589,33 @@ static int ntb_transport_setup_qp_mw(struct ntb_transport_ctx *nt,
else
num_qps_mw = qp_count / mw_count;
- rx_size = (unsigned int)mw->xlat_size / num_qps_mw;
- qp->rx_buff = mw->virt_addr + rx_size * (qp_num / mw_count);
- rx_size -= sizeof(struct ntb_rx_info);
+ mw_size = min(nt->mw_vec[mw_num].phys_size, mw->xlat_size);
+ if (max_mw_size && mw_size > max_mw_size)
+ mw_size = max_mw_size;
- qp->remote_rx_info = qp->rx_buff + rx_size;
+ /* Split this MW evenly among the queue pairs mapped to it. */
+ mw_size_per_qp = (unsigned int)mw_size / num_qps_mw;
+ qp_offset = mw_size_per_qp * (qp_num / mw_count);
+
+ /* Place remote_rx_info at the end of the per-QP region. */
+ rx_info_offset = mw_size_per_qp - sizeof(struct ntb_rx_info);
+
+ qp->tx_mw_size = mw_size_per_qp;
+ qp->tx_mw = nt->mw_vec[mw_num].vbase + qp_offset;
+ if (!qp->tx_mw)
+ return -EINVAL;
+ qp->tx_mw_phys = nt->mw_vec[mw_num].phys_addr + qp_offset;
+ if (!qp->tx_mw_phys)
+ return -EINVAL;
+ qp->rx_info = qp->tx_mw + rx_info_offset;
+ qp->rx_buff = mw->virt_addr + qp_offset;
+ qp->remote_rx_info = qp->rx_buff + rx_info_offset;
/* Due to housekeeping, there must be atleast 2 buffs */
- qp->rx_max_frame = min(transport_mtu, rx_size / 2);
- qp->rx_max_entry = rx_size / qp->rx_max_frame;
+ qp->tx_max_frame = min(transport_mtu, mw_size_per_qp / 2);
+ qp->tx_max_entry = mw_size_per_qp / qp->tx_max_frame;
+ qp->rx_max_frame = min(transport_mtu, mw_size_per_qp / 2);
+ qp->rx_max_entry = mw_size_per_qp / qp->rx_max_frame;
qp->rx_index = 0;
/*
@@ -1133,11 +1152,7 @@ static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
unsigned int qp_num)
{
struct ntb_transport_qp *qp;
- phys_addr_t mw_base;
- resource_size_t mw_size;
- unsigned int num_qps_mw, tx_size;
unsigned int mw_num, mw_count, qp_count;
- u64 qp_offset;
mw_count = nt->mw_count;
qp_count = nt->qp_count;
@@ -1152,36 +1167,6 @@ static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
qp->event_handler = NULL;
ntb_qp_link_context_reset(qp);
- if (mw_num < qp_count % mw_count)
- num_qps_mw = qp_count / mw_count + 1;
- else
- num_qps_mw = qp_count / mw_count;
-
- mw_base = nt->mw_vec[mw_num].phys_addr;
- mw_size = nt->mw_vec[mw_num].phys_size;
-
- if (max_mw_size && mw_size > max_mw_size)
- mw_size = max_mw_size;
-
- tx_size = (unsigned int)mw_size / num_qps_mw;
- qp_offset = tx_size * (qp_num / mw_count);
-
- qp->tx_mw_size = tx_size;
- qp->tx_mw = nt->mw_vec[mw_num].vbase + qp_offset;
- if (!qp->tx_mw)
- return -EINVAL;
-
- qp->tx_mw_phys = mw_base + qp_offset;
- if (!qp->tx_mw_phys)
- return -EINVAL;
-
- tx_size -= sizeof(struct ntb_rx_info);
- qp->rx_info = qp->tx_mw + tx_size;
-
- /* Due to housekeeping, there must be atleast 2 buffs */
- qp->tx_max_frame = min(transport_mtu, tx_size / 2);
- qp->tx_max_entry = tx_size / qp->tx_max_frame;
-
if (nt->debugfs_node_dir) {
char debugfs_name[8];
--
2.48.1
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