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SubjectRe: [PATCH] Intel IOMMU: RMRRs do not necessarily have to be present on all VT-d capable platforms
On Thu, 10 Jul 2008 19:53:26 -0400 Yong Wang <yong.y.wang@linux.intel.com> wrote:

> On Thu, Jul 10, 2008 at 01:01:49AM -0700, Andrew Morton wrote:
> > On Tue, 1 Jul 2008 05:13:54 -0400 Yong Wang <yong.y.wang@linux.intel.com> wrote:
> >
> > > RMRRs do not necessarily have to be present on all VT-d capable platforms.
> > > The printk is just informational and does not need to be followed by an
> > > error return.
> > >
> > > Signed-off-by: Yong Y Wang <yong.y.wang@intel.com>
> > > ---
> > > dmar.c | 4 +---
> > > 1 file changed, 1 insertion(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
> > > index f941f60..8bf86ae 100644
> > > --- a/drivers/pci/dmar.c
> > > +++ b/drivers/pci/dmar.c
> > > @@ -317,10 +317,8 @@ int __init dmar_table_init(void)
> > > return -ENODEV;
> > > }
> > >
> > > - if (list_empty(&dmar_rmrr_units)) {
> > > + if (list_empty(&dmar_rmrr_units))
> > > printk(KERN_INFO PREFIX "No RMRR found\n");
> > > - return -ENODEV;
> > > - }
> > >
> > > return 0;
> > > }
> >
> > >From your description I am unable to work out how important this fix is.
> >
> > Is it needed in 2.6.25.x? In 2.6.26? In 2.6.27? There's no way for me to
> > know :(
>
> Actually this is the same as Suresh' x2apic patch 05/26. The absence of RMRRs
> will prevent kernel from parsing IOxAPICs without this patch and thus leaves
> IOxAPICs in an uninitialized state.

And what runtime effect does that have?


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