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Message-ID: <20251129160405.2568284-22-den@valinux.co.jp>
Date: Sun, 30 Nov 2025 01:03:59 +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,
	vkoul@...nel.org,
	jdmason@...zu.us,
	dave.jiang@...el.com,
	allenbh@...il.com,
	Basavaraj.Natikar@....com,
	Shyam-sundar.S-k@....com,
	kurt.schwemmer@...rosemi.com,
	logang@...tatee.com,
	jingoohan1@...il.com,
	lpieralisi@...nel.org,
	robh@...nel.org,
	jbrunet@...libre.com,
	fancer.lancer@...il.com,
	arnd@...db.de,
	pstanner@...hat.com,
	elfring@...rs.sourceforge.net
Subject: [RFC PATCH v2 21/27] NTB: epf: Provide db_vector_count/db_vector_mask callbacks

Provide db_vector_count() and db_vector_mask() implementations for both
ntb_hw_epf and pci-epf-vntb so that ntb_transport can map MSI vectors to
doorbell bits. Without them, the upper layer cannot identify which
doorbell vector fired and ends up scheduling rxc_db_work() for all queue
pairs, resulting in a thundering-herd effect when multiple queue pairs
(QPs) are enabled.

With this change, .peer_db_set() must honor the db_bits mask and raise
all requested doorbell interrupts, so update those implementations
accordingly.

Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
 drivers/ntb/hw/epf/ntb_hw_epf.c               | 47 ++++++++++++-------
 drivers/pci/endpoint/functions/pci-epf-vntb.c | 40 +++++++++++++---
 2 files changed, 63 insertions(+), 24 deletions(-)

diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
index c94bf63d69ff..d9811da90599 100644
--- a/drivers/ntb/hw/epf/ntb_hw_epf.c
+++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
@@ -363,7 +363,7 @@ static int ntb_epf_init_isr(struct ntb_epf_dev *ndev, int msi_min, int msi_max)
 		}
 	}
 
-	ndev->db_count = irq;
+	ndev->db_count = irq - 1;
 
 	ret = ntb_epf_send_command(ndev, CMD_CONFIGURE_DOORBELL,
 				   argument | irq);
@@ -397,6 +397,22 @@ static u64 ntb_epf_db_valid_mask(struct ntb_dev *ntb)
 	return ntb_ndev(ntb)->db_valid_mask;
 }
 
+static int ntb_epf_db_vector_count(struct ntb_dev *ntb)
+{
+	return ntb_ndev(ntb)->db_count;
+}
+
+static u64 ntb_epf_db_vector_mask(struct ntb_dev *ntb, int db_vector)
+{
+	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
+
+	db_vector--; /* vector 0 is reserved for link events */
+	if (db_vector < 0 || db_vector >= ndev->db_count)
+		return 0;
+
+	return ndev->db_valid_mask & (1ULL << db_vector);
+}
+
 static int ntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
 {
 	return 0;
@@ -480,26 +496,21 @@ static int ntb_epf_peer_mw_get_addr(struct ntb_dev *ntb, int idx,
 static int ntb_epf_peer_db_set(struct ntb_dev *ntb, u64 db_bits)
 {
 	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
-	u32 interrupt_num = ffs(db_bits) + 1;
-	struct device *dev = ndev->dev;
+	u32 interrupt_num;
 	u32 db_entry_size;
 	u32 db_offset;
 	u32 db_data;
-
-	if (interrupt_num >= ndev->db_count) {
-		dev_err(dev, "DB interrupt %d greater than Max Supported %d\n",
-			interrupt_num, ndev->db_count);
-		return -EINVAL;
-	}
+	int i;
 
 	db_entry_size = readl(ndev->ctrl_reg + NTB_EPF_DB_ENTRY_SIZE);
 
-	db_data = readl(ndev->ctrl_reg + NTB_EPF_DB_DATA(interrupt_num));
-	db_offset = readl(ndev->ctrl_reg + NTB_EPF_DB_OFFSET(interrupt_num));
-
-	writel(db_data, ndev->db_reg + (db_entry_size * interrupt_num) +
-	       db_offset);
-
+	for_each_set_bit(i, (unsigned long *)&db_bits, ndev->db_count) {
+		interrupt_num = i + 1;
+		db_data = readl(ndev->ctrl_reg + NTB_EPF_DB_DATA(interrupt_num));
+		db_offset = readl(ndev->ctrl_reg + NTB_EPF_DB_OFFSET(interrupt_num));
+		writel(db_data, ndev->db_reg + (db_entry_size * interrupt_num) +
+		       db_offset);
+	}
 	return 0;
 }
 
@@ -529,6 +540,8 @@ static const struct ntb_dev_ops ntb_epf_ops = {
 	.spad_count		= ntb_epf_spad_count,
 	.peer_mw_count		= ntb_epf_peer_mw_count,
 	.db_valid_mask		= ntb_epf_db_valid_mask,
+	.db_vector_count	= ntb_epf_db_vector_count,
+	.db_vector_mask		= ntb_epf_db_vector_mask,
 	.db_set_mask		= ntb_epf_db_set_mask,
 	.mw_set_trans		= ntb_epf_mw_set_trans,
 	.mw_clear_trans		= ntb_epf_mw_clear_trans,
@@ -561,8 +574,8 @@ static int ntb_epf_init_dev(struct ntb_epf_dev *ndev)
 	int ret;
 
 	/* One Link interrupt and rest doorbell interrupt */
-	ret = ntb_epf_init_isr(ndev, NTB_EPF_MIN_DB_COUNT + NTB_EPF_IRQ_RESERVE,
-			       NTB_EPF_MAX_DB_COUNT + NTB_EPF_IRQ_RESERVE);
+	ret = ntb_epf_init_isr(ndev, NTB_EPF_MIN_DB_COUNT + 1 + NTB_EPF_IRQ_RESERVE,
+			       NTB_EPF_MAX_DB_COUNT + 1 + NTB_EPF_IRQ_RESERVE);
 	if (ret) {
 		dev_err(dev, "Failed to init ISR\n");
 		return ret;
diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 93fd724a8faa..af8753650051 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -1379,6 +1379,22 @@ static u64 vntb_epf_db_valid_mask(struct ntb_dev *ntb)
 	return BIT_ULL(ntb_ndev(ntb)->db_count) - 1;
 }
 
+static int vntb_epf_db_vector_count(struct ntb_dev *ntb)
+{
+	return ntb_ndev(ntb)->db_count;
+}
+
+static u64 vntb_epf_db_vector_mask(struct ntb_dev *ntb, int db_vector)
+{
+	struct epf_ntb *ndev = ntb_ndev(ntb);
+
+	db_vector--; /* vector 0 is reserved for link events */
+	if (db_vector < 0 || db_vector >= ndev->db_count)
+		return 0;
+
+	return 1ULL << db_vector;
+}
+
 static int vntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
 {
 	return 0;
@@ -1488,20 +1504,28 @@ static int vntb_epf_peer_spad_write(struct ntb_dev *ndev, int pidx, int idx, u32
 
 static int vntb_epf_peer_db_set(struct ntb_dev *ndev, u64 db_bits)
 {
-	u32 interrupt_num = ffs(db_bits) + 1;
 	struct epf_ntb *ntb = ntb_ndev(ndev);
 	u8 func_no, vfunc_no;
-	int ret;
+	u64 failed = 0;
+	int i;
 
 	func_no = ntb->epf->func_no;
 	vfunc_no = ntb->epf->vfunc_no;
 
-	ret = pci_epc_raise_irq(ntb->epf->epc, func_no, vfunc_no,
-				PCI_IRQ_MSI, interrupt_num + 1);
-	if (ret)
-		dev_err(&ntb->ntb.dev, "Failed to raise IRQ\n");
+	for_each_set_bit(i, (unsigned long *)&db_bits, ntb->db_count) {
+		/*
+		 * DB bit i is MSI interrupt (i + 2).
+		 * Vector 0 is used for link events and MSI vectors are
+		 * 1-based for pci_epc_raise_irq().
+		 */
+		if (pci_epc_raise_irq(ntb->epf->epc, func_no, vfunc_no,
+				      PCI_IRQ_MSI, i + 2))
+			failed |= BIT_ULL(i);
+	}
+	if (failed)
+		dev_err(&ntb->ntb.dev, "Failed to raise IRQ (0x%llx)\n", failed);
 
-	return ret;
+	return failed ? -EIO : 0;
 }
 
 static u64 vntb_epf_db_read(struct ntb_dev *ndev)
@@ -1575,6 +1599,8 @@ static const struct ntb_dev_ops vntb_epf_ops = {
 	.spad_count		= vntb_epf_spad_count,
 	.peer_mw_count		= vntb_epf_peer_mw_count,
 	.db_valid_mask		= vntb_epf_db_valid_mask,
+	.db_vector_count	= vntb_epf_db_vector_count,
+	.db_vector_mask		= vntb_epf_db_vector_mask,
 	.db_set_mask		= vntb_epf_db_set_mask,
 	.mw_set_trans		= vntb_epf_mw_set_trans,
 	.mw_clear_trans		= vntb_epf_mw_clear_trans,
-- 
2.48.1


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