linux-kernel - Re: [PATCH 1/6] NTB: epf: Avoid pci_iounmap() with offset when PEER

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Message-ID: <kc6vwcu74efffvq6v6fukwxw5dthqplhoebwjzrjeuhdhhdkx2@jwyucfzi6pq4>
Date: Sat, 25 Oct 2025 01:45:46 +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
Subject: Re: [PATCH 1/6] NTB: epf: Avoid pci_iounmap() with offset when
 PEER_SPAD and CONFIG share BAR

On Fri, Oct 24, 2025 at 11:45:12AM -0400, Frank Li wrote:
> On Thu, Oct 23, 2025 at 04:17:52PM +0900, Koichiro Den wrote:
> 
> NTB: epf: Avoid pci_iounmap() twice when PEER_SPAD and CONFIG share one BAR.
> 
> > When BAR_PEER_SPAD equals BAR_CONFIG,
> 
> When BAR_PEER_SPAD and BAR_CONFIG share one PCI BAR, ...
> > the module teardown path ends up
> > calling pci_iounmap() on the same iomem with some offset, which is
> > unnecessary and triggers a kernel warning like the following:
> >
> >   Trying to vunmap() nonexistent vm area (0000000069a5ffe8)
> >   WARNING: mm/vmalloc.c:3470 at vunmap+0x58/0x68, CPU#5: modprobe/2937
> >   [...]
> >   Call trace:
> >    vunmap+0x58/0x68 (P)
> >    iounmap+0x34/0x48
> >    pci_iounmap+0x2c/0x40
> >    ntb_epf_pci_remove+0x44/0x80 [ntb_hw_epf]
> >    pci_device_remove+0x48/0xf8
> >    device_remove+0x50/0x88
> >    device_release_driver_internal+0x1c8/0x228
> >    driver_detach+0x50/0xb0
> >    bus_remove_driver+0x74/0x100
> >    driver_unregister+0x34/0x68
> >    pci_unregister_driver+0x34/0xa0
> >    ntb_epf_pci_driver_exit+0x14/0xfe0 [ntb_hw_epf]
> >   [...]
> >
> > Fix it by unmapping only once and only the base mapping when the two
> > windows share the same BAR.
> 
> Fix it by unmapping only when PEER_SPAD and CONFIG use difference bars.

Thanks for the review and refining.

-Koichiro

> 
> Reviewed-by: Frank Li <Frank.Li@....com>
> 
> >
> > Cc: <stable@...r.kernel.org>
> > Fixes: e75d5ae8ab88 ("NTB: epf: Allow more flexibility in the memory BAR map method")
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> >  drivers/ntb/hw/epf/ntb_hw_epf.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
> > index d3ecf25a5162..9935da48a52e 100644
> > --- a/drivers/ntb/hw/epf/ntb_hw_epf.c
> > +++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
> > @@ -646,7 +646,8 @@ static void ntb_epf_deinit_pci(struct ntb_epf_dev *ndev)
> >  	struct pci_dev *pdev = ndev->ntb.pdev;
> >
> >  	pci_iounmap(pdev, ndev->ctrl_reg);
> > -	pci_iounmap(pdev, ndev->peer_spad_reg);
> > +	if (ndev->barno_map[BAR_PEER_SPAD] != ndev->barno_map[BAR_CONFIG])
> > +		pci_iounmap(pdev, ndev->peer_spad_reg);
> >  	pci_iounmap(pdev, ndev->db_reg);
> >
> >  	pci_release_regions(pdev);
> > --
> > 2.48.1
> >