Date: Tue, 5 May 2015 14:09:31 +0800
From: Dave Young <dyoung@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: "Li, Zhen-Hua" <zhen-hual@hp.com>, dwmw2@infradead.org,
        indou.takao@jp.fujitsu.com, bhe@redhat.com, vgoyal@redhat.com,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org, kexec@lists.infradead.org,
        alex.williamson@redhat.com, ddutile@redhat.com,
        ishii.hironobu@jp.fujitsu.com, bhelgaas@google.com, doug.hatch@hp.com,
        jerry.hoemann@hp.com, tom.vaden@hp.com, li.zhang6@hp.com,
        lisa.mitchell@hp.com, billsumnerlinux@gmail.com, rwright@hp.com
Subject: Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel
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 <20150504110551.GD15736@8bytes.org>
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On 05/04/15 at 01:05pm, Joerg Roedel wrote:
> On Fri, Apr 03, 2015 at 04:40:31PM +0800, Dave Young wrote:
> > Have not read all the patches, but I have a question, not sure this
> > has been answered before. Old memory is not reliable, what if the old
> > memory get corrupted before panic? Is it safe to continue using it in
> > 2nd kernel, I worry that it will cause problems.
> 
> Yes, the old memory could be corrupted, and there are more failure cases
> left which we have no way of handling yet (if iommu data structures are
> in kdump backup areas).
> 
> The question is what to do if we find some of the old data structures
> corrupted, hand how far should the tests go. Should we also check the
> page-tables, for example? I think if some of the data structures for a
> device are corrupted it probably already failed in the old kernel and
> things won't get worse in the new one.

I agree that we can do nothing with the old corrupted data, but I worry
about the future corruption after using the old corrupted data. I wonder
if we can mark all the oldmem as readonly so that we can lower the risk.
Is it resonable?

Thanks
Dave
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