linux-kernel - Re: [PATCH v3 7/7] PCI: endpoint: pci-epf-vntb: Manage ntb

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Message-ID: <aS3jVC5//QYT0DfL@lizhi-Precision-Tower-5810>
Date: Mon, 1 Dec 2025 13:49:56 -0500
From: Frank Li <Frank.li@....com>
To: Koichiro Den <den@...inux.co.jp>
Cc: ntb@...ts.linux.dev, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, jdmason@...zu.us,
	dave.jiang@...el.com, allenbh@...il.com, mani@...nel.org,
	kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com,
	jbrunet@...libre.com, lpieralisi@...nel.org, yebin10@...wei.com,
	geert+renesas@...der.be, arnd@...db.de, stable@...r.kernel.org
Subject: Re: [PATCH v3 7/7] PCI: endpoint: pci-epf-vntb: Manage ntb_dev
 lifetime and fix vpci bus teardown

On Mon, Dec 01, 2025 at 12:11:00AM +0900, Koichiro Den wrote:
> Currently ntb_dev is embedded in epf_ntb, while configfs allows starting
> or stopping controller and linking or unlinking functions as you want.
> In fact, re-linking and re-starting is not possible with the embedded
> design and leads to oopses.
>
> Allocate ntb_dev with devm and add a .remove callback to the pci driver
> that calls ntb_unregister_device(). This allows a fresh device to be
> created on the next .bind call.
>
> With these changes, the controller can now be stopped, a function
> unlinked, configfs settings updated, and the controller re-linked and
> restarted without rebooting the endpoint, as long as the underlying
> pci_epc_ops .stop() operation is non-destructive, and .start() can
> restore normal operations.
>
> Signed-off-by: Koichiro Den <den@...inux.co.jp>
> ---
>  drivers/pci/endpoint/functions/pci-epf-vntb.c | 52 ++++++++++++++-----
>  1 file changed, 39 insertions(+), 13 deletions(-)
...
> @@ -1097,7 +1103,6 @@ static int vpci_scan_bus(void *sysdata)
>  {
>  	struct pci_bus *vpci_bus;
>  	struct epf_ntb *ndev = sysdata;
> -

Unneccsary change here.

Frank Li

>  	LIST_HEAD(resources);
>  	static struct resource busn_res = {
>  		.start = 0,
> @@ -1115,6 +1120,7 @@ static int vpci_scan_bus(void *sysdata)
>  		pr_err("create pci bus failed\n");
>  		return -EINVAL;
>  	}
> +	ndev->vpci_bus = vpci_bus;
>
>  	pci_bus_add_devices(vpci_bus);
>
> @@ -1159,7 +1165,7 @@ static int vntb_epf_mw_set_trans(struct ntb_dev *ndev, int pidx, int idx,
>  	int ret;
>  	struct device *dev;
>
> -	dev = &ntb->ntb.dev;
> +	dev = &ntb->ntb->dev;
>  	barno = ntb->epf_ntb_bar[BAR_MW1 + idx];
>  	epf_bar = &ntb->epf->bar[barno];
>  	epf_bar->phys_addr = addr;
> @@ -1259,7 +1265,7 @@ static int vntb_epf_peer_db_set(struct ntb_dev *ndev, u64 db_bits)
>  	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");
> +		dev_err(&ntb->ntb->dev, "Failed to raise IRQ\n");
>
>  	return ret;
>  }
> @@ -1346,9 +1352,12 @@ static int pci_vntb_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	struct epf_ntb *ndev = (struct epf_ntb *)pdev->sysdata;
>  	struct device *dev = &pdev->dev;
>
> -	ndev->ntb.pdev = pdev;
> -	ndev->ntb.topo = NTB_TOPO_NONE;
> -	ndev->ntb.ops =  &vntb_epf_ops;
> +	ndev->ntb = devm_kzalloc(dev, sizeof(*ndev->ntb), GFP_KERNEL);
> +	if (!ndev->ntb)
> +		return -ENOMEM;
> +	ndev->ntb->pdev = pdev;
> +	ndev->ntb->topo = NTB_TOPO_NONE;
> +	ndev->ntb->ops = &vntb_epf_ops;
>
>  	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
>  	if (ret) {
> @@ -1356,7 +1365,7 @@ static int pci_vntb_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  		return ret;
>  	}
>
> -	ret = ntb_register_device(&ndev->ntb);
> +	ret = ntb_register_device(ndev->ntb);
>  	if (ret) {
>  		dev_err(dev, "Failed to register NTB device\n");
>  		return ret;
> @@ -1366,6 +1375,17 @@ static int pci_vntb_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	return 0;
>  }
>
> +static void pci_vntb_remove(struct pci_dev *pdev)
> +{
> +	struct epf_ntb *ndev = (struct epf_ntb *)pdev->sysdata;
> +
> +	if (!ndev || !ndev->ntb)
> +		return;
> +
> +	ntb_unregister_device(ndev->ntb);
> +	ndev->ntb = NULL;
> +}
> +
>  static struct pci_device_id pci_vntb_table[] = {
>  	{
>  		PCI_DEVICE(0xffff, 0xffff),
> @@ -1377,6 +1397,7 @@ static struct pci_driver vntb_pci_driver = {
>  	.name           = "pci-vntb",
>  	.id_table       = pci_vntb_table,
>  	.probe          = pci_vntb_probe,
> +	.remove         = pci_vntb_remove,
>  };
>
>  /* ============ PCIe EPF Driver Bind ====================*/
> @@ -1459,10 +1480,15 @@ static void epf_ntb_unbind(struct pci_epf *epf)
>  {
>  	struct epf_ntb *ntb = epf_get_drvdata(epf);
>
> +	pci_unregister_driver(&vntb_pci_driver);
> +
> +	pci_lock_rescan_remove();
> +	pci_stop_root_bus(ntb->vpci_bus);
> +	pci_remove_root_bus(ntb->vpci_bus);
> +	pci_unlock_rescan_remove();
> +
>  	epf_ntb_epc_cleanup(ntb);
>  	epf_ntb_config_spad_bar_free(ntb);
> -
> -	pci_unregister_driver(&vntb_pci_driver);
>  }
>
>  // EPF driver probe
> --
> 2.48.1
>