linux-kernel - Re: [Xen-devel] crash tool - problem with new Xen linear virtual mapped sparse p2m list

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Date:	Tue, 24 Nov 2015 10:09:01 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Malcolm Crossley <malcolm.crossley@...rix.com>,
	Jan Beulich <JBeulich@...e.com>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	Juergen Gross <JGross@...e.com>
CC:	<olaf@...fle.de>, <keir@....org>, <andrew.cooper3@...rix.com>,
	<ptesarik@...e.cz>, <linux-kernel@...r.kernel.org>,
	<dslutz@...izon.com>, <anderson@...hat.com>,
	David Mair <DMAIR@...e.com>, <xen-devel@...ts.xenproject.org>,
	<boris.ostrovsky@...cle.com>, <crash-utility@...hat.com>
Subject: Re: [Xen-devel] crash tool - problem with new Xen linear virtual
 mapped sparse p2m list

On 24/11/15 09:55, Malcolm Crossley wrote:
> On 24/11/15 08:59, Jan Beulich wrote:
>>>>> On 24.11.15 at 07:55, <JGross@...e.com> wrote:
>>> What about:
>>>
>>> 4) Instead of relying on the kernel maintained p2m list for m2p
>>>    conversion use the hypervisor maintained m2p list which should be
>>>    available in the dump as well. This is the way the alive kernel is
>>>    working, so mimic it during crash dump analysis.
>>
>> I fully agree; I have to admit that looking at the p2m when doing page
>> table walks for a PV Dom0 (having all machine addresses in page table
>> entries) seems kind of backwards. (But I say this knowing nothing
>> about the tool.)
>>
> I don't think we can reliably use the m2p for PV domains because
> PV domains don't always issue a m2p update hypercall when they change
> their p2m mapping.

This only applies to foreign pages which won't be very interesting to a
crash tool.

David
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