linux-kernel - Re: [patch 1/2] Intel IOMMU Suspend/Resume Support for DMAR

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Date:	Wed, 25 Mar 2009 23:47:07 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	fenghua.yu@...el.com, amluto@...il.com, kyle@...hat.com,
	mgross@...ux.intel.com, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org
Subject: Re: [patch 1/2] Intel IOMMU Suspend/Resume Support for DMAR

On Wed, 2009-03-25 at 21:12 +0100, Ingo Molnar wrote:
> 
> > +static int iommu_resume(struct sys_device *dev)
> > +{
> > +     struct dmar_drhd_unit *drhd;
> > +     struct intel_iommu *iommu;
> > +     unsigned long flag;
> > +     int i = 0;
> > +
> > +     if (init_iommu_hw())
> > +             panic("IOMMU setup failed, DMAR can not start!\n");
> 
> Please dont panic boxes ... insert a WARN() and return.

Well, the box is going to die anyway. If it was using the IOMMU before
suspend, and you fail to re-initialise the IOMMU after resume, then
you're buggered.

But if you panic() immediately during the resume, the message is
unlikely to make it out even to a serial console. If you print a warning
and limp on, I suppose there's at least a _chance_ that it might get
seen.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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