2.6.39-stable review patch.  If anyone has any objections, please let us know.

------------------
 function

From: Mike Travis <[email protected]>

commit cb452a4040bb051d92e85d6e7eb60c11734c1781 upstream.

When there are a large count of PCI devices, and the pass through
option for iommu is set, much time is spent in the identity_mapping
function hunting though the iommu domains to check if a specific
device is "identity mapped".

Speed up the function by checking the cached info to see if
it's mapped to the static identity domain.

Signed-off-by: Mike Travis <[email protected]>
Reviewed-by: Mike Habeck <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/pci/intel-iommu.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -2109,10 +2109,10 @@ static int identity_mapping(struct pci_d
        if (likely(!iommu_identity_mapping))
                return 0;
 
+       info = pdev->dev.archdata.iommu;
+       if (info && info != DUMMY_DEVICE_DOMAIN_INFO)
+               return (info->domain == si_domain);
 
-       list_for_each_entry(info, &si_domain->devices, link)
-               if (info->dev == pdev)
-                       return 1;
        return 0;
 }
 


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