Re: [PATCH 1/2] x86/amd-iommu: enable iommu before attachingdevices

From: Chris Wright
Date: Thu Apr 01 2010 - 21:39:42 EST

* Neil Horman (nhorman@xxxxxxxxxx) 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@xxxxxxxxxxxxx>
> > Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
> > Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
> 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.

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