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

[Mike Travis <travis@sgi.com>]

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;
 }