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

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Message-ID: <aPufCHOKK7WrBKR+@lizhi-Precision-Tower-5810>
Date: Fri, 24 Oct 2025 11:45:12 -0400
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
Subject: Re: [PATCH 1/6] NTB: epf: Avoid pci_iounmap() with offset when
 PEER_SPAD and CONFIG share BAR

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.

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
>