linux-kernel - Re: [PATCH 1/2] x86/amd-iommu: enable iommu before attaching devices

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Date:	Thu, 1 Apr 2010 18:38:27 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Neil Horman <nhorman@...hat.com>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	Joerg Roedel <joerg.roedel@....com>,
	Neil Horman <nhorman@...driver.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, hbabu@...ibm.com,
	iommu@...ts.linux-foundation.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH 1/2] x86/amd-iommu: enable iommu before attaching
	devices

* Neil Horman (nhorman@...hat.com) wrote:
> On Thu, Apr 01, 2010 at 06:23:53PM -0700, Chris Wright wrote:
> > Hit another kdump problem as reported by Neil Horman.  When initializaing
> > the IOMMU, we attach devices to their domains before the IOMMU is
> > fully (re)initialized.  Attaching a device will issue some important
> > invalidations.  In the context of the newly kexec'd kdump kernel, the
> > IOMMU may have stale cached data from the original kernel.  Because we
> > do the attach too early, the invalidation commands are placed in the new
> > command buffer before the IOMMU is updated w/ that buffer.  This leaves
> > the stale entries in the kdump context and can renders device unusable.
> > Simply enable the IOMMU before we do the attach.
> > 
> > Cc: Neil Horman <nhorman@...driver.com>
> > Cc: Vivek Goyal <vgoyal@...hat.com>
> > Signed-off-by: Chris Wright <chrisw@...s-sol.org>
> 
> I'll test this out this weekend, thanks Chris!

Great, thanks!  I tested w/ both default and iommu=pt.  Both worked,
didn't spot any regressions.  But additional testing is very welcome.

thanks,
-chris
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