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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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