From: Dave Young <dyoung@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: luyu@redhat.com, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
horms@verge.net.au, vgoyal@redhat.com
Subject: Re: [PATCH retry] intel-iommu:make identity_map default for crash dump
Date: Tue, 01 Nov 2011 17:52:28 +0800 [thread overview]
Message-ID: <4EAFC15C.7010601@redhat.com> (raw)
In-Reply-To: <1320140052.2089.5.camel@shinybook.infradead.org>
On 11/01/2011 05:34 PM, David Woodhouse wrote:
> On Tue, 2011-11-01 at 17:19 +0800, Dave Young wrote:
>> kdump kernel sometimes will get DMAR faults which
>> is caused by random in-flight dma from 1st kernel
>>
>> Here make the identity_mapping as default for this case
>
> So you want to *allow* the random in-flight DMA? And with an identity
> mapping it's really going to random addresses, since it'll be
> untranslated and won't even go to the physical addresses which it was
> originally intended for?
>
> This seems entirely broken to me.
>
> If there is "random in-flight dma" from the first kernel, the correct
> thing to do is *block* it. Which is what we do.
>
This patch works for me for several cases. For kdump It can be seen a
workaround. But yes blocking the 1st kernel dma is ideal.
Glad to hear that you are working on this.
--
Thanks
Dave
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Young <dyoung@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: kexec@lists.infradead.org, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, vgoyal@redhat.com,
horms@verge.net.au, luyu@redhat.com
Subject: Re: [PATCH retry] intel-iommu:make identity_map default for crash dump
Date: Tue, 01 Nov 2011 17:52:28 +0800 [thread overview]
Message-ID: <4EAFC15C.7010601@redhat.com> (raw)
In-Reply-To: <1320140052.2089.5.camel@shinybook.infradead.org>
On 11/01/2011 05:34 PM, David Woodhouse wrote:
> On Tue, 2011-11-01 at 17:19 +0800, Dave Young wrote:
>> kdump kernel sometimes will get DMAR faults which
>> is caused by random in-flight dma from 1st kernel
>>
>> Here make the identity_mapping as default for this case
>
> So you want to *allow* the random in-flight DMA? And with an identity
> mapping it's really going to random addresses, since it'll be
> untranslated and won't even go to the physical addresses which it was
> originally intended for?
>
> This seems entirely broken to me.
>
> If there is "random in-flight dma" from the first kernel, the correct
> thing to do is *block* it. Which is what we do.
>
This patch works for me for several cases. For kdump It can be seen a
workaround. But yes blocking the 1st kernel dma is ideal.
Glad to hear that you are working on this.
--
Thanks
Dave
next prev parent reply other threads:[~2011-11-01 9:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-01 9:19 [PATCH retry] intel-iommu:make identity_map default for crash dump Dave Young
2011-11-01 9:19 ` Dave Young
2011-11-01 9:34 ` David Woodhouse
2011-11-01 9:34 ` David Woodhouse
2011-11-01 9:52 ` Dave Young [this message]
2011-11-01 9:52 ` Dave Young
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