[RFC PATCH v4 08/38] NTB: epf: Provide db_vector_count/db_vector_mask callbacks

Koichiro Den
2026-01-18T13:55:12Z

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@valinux.co.jp>
---
drivers/ntb/hw/epf/ntb_hw_epf.c | 47 ++++++++++++-------
drivers/pci/endpoint/functions/pci-epf-vntb.c | 41 +++++++++++++---
2 files changed, 64 insertions(+), 24 deletions(-)

diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
index dbb5bebe63a5..c37ede4063dc 100644
--- a/drivers/ntb/hw/epf/ntb_hw_epf.c
+++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
@@ -381,7 +381,7 @@ 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);
@@ -415,6 +415,22 @@ 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 & BIT_ULL(db_vector);
+}
+
static int ntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
{
return 0;
@@ -507,26 +523,21 @@ 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;
- }
+ unsigned long 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;
}

@@ -556,6 +567,8 @@ 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,
@@ -607,8 +620,8 @@ 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 4927faa28255..39e784e21236 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -1384,6 +1384,22 @@ 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 BIT_ULL(db_vector);
+}
+
static int vntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
{
return 0;
@@ -1487,20 +1503,29 @@ 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;
+ unsigned long 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 (%#llx)\n",
+ failed);

- return ret;
+ return failed ? -EIO : 0;
}

static u64 vntb_epf_db_read(struct ntb_dev *ndev)
@@ -1561,6 +1586,8 @@ 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,
--
2.51.0