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Message-ID: <4EAFC15C.7010601@redhat.com> Date: Tue, 01 Nov 2011 17:52:28 +0800 From: Dave Young <dyoung@...hat.com> To: David Woodhouse <dwmw2@...radead.org> CC: kexec@...ts.infradead.org, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, vgoyal@...hat.com, horms@...ge.net.au, luyu@...hat.com Subject: Re: [PATCH retry] intel-iommu:make identity_map default for crash dump 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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