linux-kernel - Re: [PATCH v3 6/7] PCI: endpoint: pci-epf-vntb: Switch vpci_scan_bus() to use pci_scan_root

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Message-ID: <kmaxwuo6diytlbtarf7pigl7v5zgslhmgnxhvujfds7kecmxbj@co4oo6lytb3o>
Date: Tue, 2 Dec 2025 16:11:55 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
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 6/7] PCI: endpoint: pci-epf-vntb: Switch
 vpci_scan_bus() to use pci_scan_root_bus()

On Mon, Dec 01, 2025 at 01:51:49PM -0500, Frank Li wrote:
> On Mon, Dec 01, 2025 at 12:10:59AM +0900, Koichiro Den wrote:
> > vpci_scan_bus() currently uses pci_scan_bus(), which creates a root bus
> > without a parent struct device. In a subsequent change we want to tear
> > down the virtual PCI root bus using pci_remove_root_bus(). For that to
> > work correctly, the root bus must be associated with a parent device,
> > similar to what the removed pci_scan_bus_parented() helper used to do.
> >
> > Switch vpci_scan_bus() to use pci_scan_root_bus() and pass
> > &ndev->epf->epc->dev as the parent. Build the resource list in the same
> > way as pci_scan_bus(), so the behavior is unchanged except that the
> > virtual root bus now has a proper parent device. This avoids crashes in
> > the pci_epf_unbind() -> epf_ntb_unbind() -> pci_remove_root_bus() ->
> > pci_bus_release_domain_nr() path once we start removing the root bus in
> > a follow-up patch.
> >
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> >  drivers/pci/endpoint/functions/pci-epf-vntb.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > index 750a246f79c9..af0651c03b20 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > @@ -1098,7 +1098,19 @@ static int vpci_scan_bus(void *sysdata)
> >  	struct pci_bus *vpci_bus;
> >  	struct epf_ntb *ndev = sysdata;
> >
> 
> next patch's remove empty line should be in this patch.

Sorry for the noise. Please let me send v4.
Thank you for the careful review.

-Koichiro

> 
> Reviewed-by: Frank Li <Frank.Li@....com>
> 
> Frank
> > -	vpci_bus = pci_scan_bus(ndev->vbus_number, &vpci_ops, sysdata);
> > +	LIST_HEAD(resources);
> > +	static struct resource busn_res = {
> > +		.start = 0,
> > +		.end = 255,
> > +		.flags = IORESOURCE_BUS,
> > +	};
> > +
> > +	pci_add_resource(&resources, &ioport_resource);
> > +	pci_add_resource(&resources, &iomem_resource);
> > +	pci_add_resource(&resources, &busn_res);
> > +
> > +	vpci_bus = pci_scan_root_bus(&ndev->epf->epc->dev, ndev->vbus_number,
> > +				     &vpci_ops, sysdata, &resources);
> >  	if (!vpci_bus) {
> >  		pr_err("create pci bus failed\n");
> >  		return -EINVAL;
> > --
> > 2.48.1
> >