linux-kernel - Re: [PATCH v11 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

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Message-ID: <5578042D.9050407@hp.com>
Date:	Wed, 10 Jun 2015 17:32:29 +0800
From:	"Li, ZhenHua" <zhen-hual@...com>
To:	Joerg Roedel <joro@...tes.org>
CC:	David Woodhouse <dwmw2@...radead.org>, bhe@...hat.com,
	tom.vaden@...com, rwright@...com, linux-pci@...r.kernel.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	lisa.mitchell@...com, iommu@...ts.linux-foundation.org,
	doug.hatch@...com, ishii.hironobu@...fujitsu.com,
	bhelgaas@...gle.com, billsumnerlinux@...il.com, li.zhang6@...com,
	dyoung@...hat.com, vgoyal@...hat.com,
	"Li, ZhenHua" <zhen-hual@...com>
Subject: Re: [PATCH v11 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

On 06/10/2015 05:21 PM, Joerg Roedel wrote:
> On Tue, Jun 09, 2015 at 01:55:50PM +0100, David Woodhouse wrote:
>> On Mon, 2015-06-08 at 18:13 +0200, Joerg Roedel wrote:
>>> So I think we need to read out that bit when we find translation enabled
>>> and if it is different from what we would set it to, we bail out of any
>>> copying, disable translation and proceed as in a normal boot.
>>
>> Given that this is only for kdump and not the general case of kexec,
>> that's probably tolerable. Of course we do still need to make it *not*
>> broken for the case where DMA_RTADDR_RTT is set, as it is at the
>> moment.
>
> Yes, I just sent a patch for this and will include it into my x86/vt-d
> branch if not objections come in.
>
>> And I suspect if we're doing that, it might be simple enough to make it
>> convert to/from the extended page tables. I don't think we want to
>> preserve PASID tables; only the "second level" (i.e. traditional)
>> translation. So we could happily pull the page table pointer out of
>> either kind of context entry, and install it into either kind. I think
>> there's a simple mapping of translation types too. I need to sort out
>> the translation types when adding the real PASID support (imminently!)
>> anyway.
>
> What happens when we take away the PASID tables from a device? Can it
> also go into some failure state?
> When doing this, we need at least setup the page request queue before we
> copy over anything and change the root-entry. Then we can handle any
> faults that are caused by this and tell the device to not try further.
>
>
> 	Joerg
>
Is PASID part of new specs? Is there any plan to upgrade the driver to 
support the latest vt-d specs?

Zhenhua

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