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

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Date:	Thu, 26 Mar 2009 10:58:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	David Woodhouse <dwmw2@...radead.org>
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


* David Woodhouse <dwmw2@...radead.org> wrote:

> 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.

except if one is testing suspend/resume (via pm-test) without 
actually suspending the hardware.

> 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.

yeah.

	Ingo
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