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

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Date:	14 Mar 2007 22:46:47 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Tejun Heo <htejun@...il.com>
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

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? 

-Andi
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