linux-kernel - [05/89] intel-iommu: Speed up processing of the identity

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Message-Id: <20110616000229.482757566@clark.kroah.org>
Date:	Wed, 15 Jun 2011 16:59:28 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Mike Travis <travis@....com>,
	David Woodhouse <David.Woodhouse@...el.com>
Subject: [05/89] intel-iommu: Speed up processing of the identity_mapping

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

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

From: Mike Travis <travis@....com>

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@....com>
Reviewed-by: Mike Habeck <habeck@....com>
Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 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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