linux-kernel - Re: [PATCH/RFC] PCI prepare/activate instead of enable to avoid IRQ storm and rogue DMA access

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Date:	Thu, 15 Mar 2007 11:39:58 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	gregkh@...e.de, Jeff Garzik <jeff@...zik.org>,
	linux-kernel@...r.kernel.org, linux-pci@...ey.karlin.mff.cuni.cz,
	michal.k.k.piotrowski@...il.com, linux-ide@...r.kernel.org,
	tglx@...utronix.de, shemminger@...ux-foundation.org,
	mlord@...ox.com, linux-pm@...ts.osdl.org
Subject: Re: [PATCH/RFC] PCI prepare/activate instead of enable to avoid IRQ
 storm and rogue DMA access

Andi Kleen wrote:
> Tejun Heo <htejun@...il.com> writes:
>> Let's assume there's a device which shares its INTX IRQ line with
>> another device and the other one is already initialized.  During boot,
>> due to BIOS's fault, bad hardware design or sheer bad luck, the device
>> has got a pending IRQ.
> 
> This seems to be also common after kexec during kexec crashdumps
> where the device just continues doing what it did before the crash.
> 
>> This patch expands the pci_set_master() approach.  Instead of enabling
>> the device in one go, it's done in two steps - prepare and activate.
>> 'prepare' enables access to PCI configuration,
> 
> I hope there aren't any new erratas triggered by this. Perhaps it would
> make sense to add some paranoia sleeps at least before touching other
> state? 

Do you mean between disabling IRQ mechanisms and enabling PCI device in 
pcim_prepare_device()?

Thanks.

-- 
tejun
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