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Date: Tue, 17 Mar 2026 14:08:11 +0100
From: Lukas Wunner <lukas@wunner.de>
To: Benjamin Block <bblock@linux.ibm.com>
Cc: Benjamin Block <lkml@mageta.org>, Guenter Roeck <linux@roeck-us.net>,
	Niklas Schnelle <schnelle@linux.ibm.com>,
	Ionut Nechita <ionut.nechita@windriver.com>,
	Bjorn Helgaas <helgaas@kernel.org>, Keith Busch <kbusch@kernel.org>,
	Gerd Bayer <gbayer@linux.ibm.com>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Halil Pasic <pasic@linux.ibm.com>, Farhan Ali <alifm@linux.ibm.com>,
	Julian Ruess <julianr@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/2] PCI/IOV: Fix race between SR-IOV enable/disable
 and hotplug
Message-ID: <ablSO1rA8D2blipG@wunner.de>
References: <20251216-revert_sriov_lock-v3-0-dac4925a7621@linux.ibm.com>
 <20251216-revert_sriov_lock-v3-2-dac4925a7621@linux.ibm.com>
 <0ca9e675-478c-411d-be32-e2d81439288f@roeck-us.net>
 <20260317090149.GA3835708@chlorum.ategam.org>
 <20260317094656.GI2161595@p1gen4-pw042f0m>
 <20260317113334.GJ2161595@p1gen4-pw042f0m>
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In-Reply-To: <20260317113334.GJ2161595@p1gen4-pw042f0m>

On Tue, Mar 17, 2026 at 12:33:34PM +0100, Benjamin Block wrote:
> @@ -518,8 +520,13 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
>  	if (kstrtoul(buf, 0, &val) < 0)
>  		return -EINVAL;
>  
> -	if (val && device_remove_file_self(dev, attr))
> +	if (val && device_remove_file_self(dev, attr)) {
> +		device_lock(dev);
> +		kill_device(dev);
> +		device_unlock(dev);
> +		device_driver_detach(dev);
>  		pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
> +	}
>  	return count;
>  }
>  static DEVICE_ATTR_IGNORE_LOCKDEP(remove, 0220, NULL,
> 
> Marking the device dead prevents re-binding after the unbind.

That can also be achieved through the PCI_DEV_ALLOW_BINDING flag,
though you'd have to add a pci_dev_disallow_binding() helper in
drivers/pci/pci.h to go alongside the existing
pci_dev_allow_binding() and pci_dev_binding_disallowed() helpers.

However pci_stop_and_remove_bus_device() implicitly unbinds the
driver before removing the device.  Remind me, what's the need
to unbind before calling that function?

Thanks,

Lukas