linux-kernel - Re: [PATCH v2 3/3] x86/quirks: Add early quirk to reset Apple AirPort card

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Date:	Sun, 12 Jun 2016 13:49:02 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Lukas Wunner <lukas@...ner.de>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 3/3] x86/quirks: Add early quirk to reset Apple
 AirPort card


* Lukas Wunner <lukas@...ner.de> wrote:

> The solution is to reset the card on boot by writing to a reset bit in
> its mmio space. This must be done as an early quirk and not as a plain
> vanilla PCI quirk to successfully combat memory corruption by DMAed
> packets: Matthew Garrett found out in 2012 that the packets are written
> to EfiBootServicesData memory (http://mjg59.dreamwidth.org/11235.html).
> This type of memory is made available to the page allocator by
> efi_free_boot_services(). [...]

Btw., would it also make sense to *not* free those pages by default, if firmware 
can occasionally corrupt them? What memory size are we talking about?

Thanks,

	Ingo