linux-kernel - Re: [PATCHv3 0/6] Crashdump Accepting Active IOMMU

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Date:	Tue, 08 Apr 2014 17:14:46 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Don Dutile <ddutile@...hat.com>
Cc:	Bill Sumner <bill.sumner@...com>, indou.takao@...fujitsu.com,
	bhe@...hat.com, joro@...tes.org, iommu@...ts.linux-foundation.org,
	kexec@...ts.infradead.org, alex.williamson@...hat.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, zhenhua@...com
Subject: Re: [PATCHv3 0/6] Crashdump Accepting Active IOMMU

On Mon, 2014-04-07 at 16:43 -0400, Don Dutile wrote:
> 
> Additionally, a tidbit of information like "some servers force NMI's
> on DMAR faults,
> and cause a system reset, thereby, preventing a kdump to occur"
> should have been included as one reason to stop DMAR faults from
> occurring on kexec-boot,
> in addition to the fact that a flood of them can lock up a system.

How about allocating a physical scratch page, and setting up a mapping
for each device such that *every* virtual address (apart from those
listed in RMRRs, perhaps) is mapped to that same scratch page?

That way you avoid the faults, but you also avoid stray DMA to parts of
the system that you don't want to get corrupted.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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