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

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Message-ID: <53444330.2030606@redhat.com>
Date:	Tue, 08 Apr 2014 14:42:56 -0400
From:	Don Dutile <ddutile@...hat.com>
To:	David Woodhouse <dwmw2@...radead.org>
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 04/08/2014 12:14 PM, David Woodhouse wrote:
> 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.
>
+1... more isolation as second kernel booting sounds good.

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