linux-kernel - Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

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Message-ID: <20150512055707.GB29874@localhost.localdomain>
Date:	Tue, 12 May 2015 13:57:07 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	"Li, Zhen-Hua" <zhen-hual@...com>, dwmw2@...radead.org,
	indou.takao@...fujitsu.com, bhe@...hat.com, vgoyal@...hat.com,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kexec@...ts.infradead.org,
	alex.williamson@...hat.com, ddutile@...hat.com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, jerry.hoemann@...com, tom.vaden@...com,
	li.zhang6@...com, lisa.mitchell@...com, billsumnerlinux@...il.com,
	rwright@...com
Subject: Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

On 05/11/15 at 12:11pm, Joerg Roedel wrote:
> On Thu, May 07, 2015 at 09:56:00PM +0800, Dave Young wrote:
> > Joreg, I can not find the last reply from you, so just reply here about
> > my worries here.
> > 
> > I said that the patchset will cause more problems, let me explain about
> > it more here:
> > 
> > Suppose page table was corrupted, ie. original mapping iova1 -> page 1
> > it was changed to iova1 -> page 2 accidently while crash happening,
> > thus future dma will read/write page 2 instead page 1, right?
> 
> When the page-table is corrupted then it is a left-over from the old
> kernel. When the kdump kernel boots the situation can at least not get
> worse. For the page tables it is also hard to detect wrong mappings (if
> this would be possible the hardware could already do it), so any checks
> we could do there are of limited use anyway.

Joerg, since both of you guys do not think it is a problem I will object it 
any more though I still do not like reusing the old page tables. So let's
leave it as a future issue.

Thanks
Dave
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