linux-kernel - Re: [Bugfix] x86/PCI: Release PCI IRQ resource only if PCI device is disabled when unbinding

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Date:	Fri, 13 Mar 2015 22:45:18 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Alex Williamson <alex.williamson@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	"bp @ alien8 . de" <bp@...en8.de>, Lv Zheng <lv.zheng@...el.com>,
	"yinghai @ kernel . org" <yinghai@...nel.org>,
	"lenb @ kernel . org" <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [Bugfix] x86/PCI: Release PCI IRQ resource only if PCI device is disabled when unbinding

On Friday, March 13, 2015 10:06:43 AM Jiang Liu wrote:
> To support IOAPIC hot-removal, we need to release PCI interrupt resource
> when unbinding PCI device driver. But due to historical reason,
> /*
>  * We would love to complain here if pci_dev->is_enabled is set, that
>  * the driver should have called pci_disable_device(), but the
>  * unfortunate fact is there are too many odd BIOS and bridge setups
>  * that don't like drivers doing that all of the time.
>  * Oh well, we can dream of sane hardware when we sleep, no matter how
>  * horrible the crap we have to deal with is when we are awake...
>  */
> some drivers don't call pci_disable_device() when unloading, which
> prevents us from reallocating PCI interrupt resource on reloading
> PCI driver and causes regressions.
> 
> So release PCI interrupt resource only if PCI device is disabled when
> unbinding. By this way, we could support IOAPIC hot-removal on latest
> platforms and avoid regressions on old platforms.
> 
> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>

OK, I can agree with that.

Bjorn, what do you think?

> ---
>  arch/x86/pci/common.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index 3d2612b68694..8d792142cb2a 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -527,7 +527,7 @@ static int pci_irq_notifier(struct notifier_block *nb, unsigned long action,
>  	if (action != BUS_NOTIFY_UNBOUND_DRIVER)
>  		return NOTIFY_DONE;
>  
> -	if (pcibios_disable_irq)
> +	if (!pci_is_enabled(dev) && pcibios_disable_irq)
>  		pcibios_disable_irq(dev);
>  
>  	return NOTIFY_OK;
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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