[05/89] intel-iommu: Speed up processing of the identity_mapping

From: Greg KH
Date: Thu Jun 16 2011 - 03:42:02 EST

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


From: Mike Travis <travis@xxxxxxx>

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 <travis@xxxxxxx>
Reviewed-by: Mike Habeck <habeck@xxxxxxx>
Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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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