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Message-ID: <aW6N+6r/Cy+VOYnW@lizhi-Precision-Tower-5810>
Date: Mon, 19 Jan 2026 15:03:07 -0500
From: Frank Li <Frank.li@....com>
To: Koichiro Den <den@...inux.co.jp>
Cc: dave.jiang@...el.com, cassel@...nel.org, mani@...nel.org,
kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com,
geert+renesas@...der.be, robh@...nel.org, vkoul@...nel.org,
jdmason@...zu.us, allenbh@...il.com, jingoohan1@...il.com,
lpieralisi@...nel.org, linux-pci@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
dmaengine@...r.kernel.org, iommu@...ts.linux.dev,
ntb@...ts.linux.dev, netdev@...r.kernel.org,
linux-kselftest@...r.kernel.org, arnd@...db.de,
gregkh@...uxfoundation.org, joro@...tes.org, will@...nel.org,
robin.murphy@....com, magnus.damm@...il.com, krzk+dt@...nel.org,
conor+dt@...nel.org, corbet@....net, skhan@...uxfoundation.org,
andriy.shevchenko@...ux.intel.com, jbrunet@...libre.com,
utkarsh02t@...il.com
Subject: Re: [RFC PATCH v4 08/38] NTB: epf: Provide
db_vector_count/db_vector_mask callbacks
On Sun, Jan 18, 2026 at 10:54:10PM +0900, Koichiro Den wrote:
> 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>
> ---
Patch 6/7/8 can be post seperatly. Basic look good.
Frank
> 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
>
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