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SubjectRe: [PATCH 2/4] Intel iommu: Speed up processing of the identity_mapping function v2
Subject: Intel iommu: Speed up processing of the identity_mapping function

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@sgi.com>
---
drivers/pci/intel-iommu.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- linux-2.6.32.orig/drivers/pci/intel-iommu.c
+++ linux-2.6.32/drivers/pci/intel-iommu.c
@@ -2124,10 +2124,10 @@ 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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