Message-ID: <513E36FA.3030905@zytor.com>
Date: Mon, 11 Mar 2013 12:56:42 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: "Eric W. Biederman" <ebiederm@xmission.com>
CC: Yinghai Lu <yinghai@kernel.org>, Vivek Goyal <vgoyal@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        WANG Chao <chaowang@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86, kdump: Set crashkernel_low automatically
References: <513D52BA.3070206@redhat.com> <1362977817-23297-1-git-send-email-yinghai@kernel.org> <20130311144853.GB8482@redhat.com> <20130311150256.GC8482@redhat.com> <CAE9FiQW1CHJ-j9aFgdtKEsgyZSTHTS1HzgMSGM8FnV7Ns3kUvw@mail.gmail.com> <20130311182655.GB12107@redhat.com> <513E2695.3080707@zytor.com> <CAE9FiQXLodhSFy4T9pKLMS+axF0jHGL9B0+TL=dYOFrLVudN9g@mail.gmail.com> <513E28B8.3000502@zytor.com> <87r4jllpfb.fsf@xmission.com>
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On 03/11/2013 12:14 PM, Eric W. Biederman wrote:
> 
> I don't totally follow the reasoning, but there is one real motivating
> example that is not easy to fix and it has little to do with
> kexec-tools.  There is a practical issue that so far the easiest way
> to deal with iommus after a kexec on panic is to just not use them.
> The problem is what to do with existing DMAs transfers that were setup
> by the kernel that crashed and are using the iommu.
> 
> When you are loaded above 4G not using iommus can be a challenge.
> 

Isn't that what swiotlb is for?

	-hpa

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