linux-kernel - [PATCH] iommu/vt-d: reduce extra first level entry in iommu->domains

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Date:	Sat, 21 May 2016 02:41:51 +0000
From:	Wei Yang <richard.weiyang@...il.com>
To:	joro@...tes.org
Cc:	dwmw2@...radead.org, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, Wei Yang <richard.weiyang@...il.com>
Subject: [PATCH] iommu/vt-d: reduce extra first level entry in iommu->domains

In commit <8bf478163e69> ("iommu/vt-d: Split up iommu->domains array"), it
it splits iommu->domains in two levels. Each first level contains 256
entries of second level. In case of the ndomains is exact a multiple of
256, it would have one more extra first level entry for current
implementation.

This patch refines this calculation to reduce the extra first level entry.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
---
 drivers/iommu/intel-iommu.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index e3061d3..2204ca4 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1634,7 +1634,7 @@ static int iommu_init_domains(struct intel_iommu *iommu)
 		return -ENOMEM;
 	}
 
-	size = ((ndomains >> 8) + 1) * sizeof(struct dmar_domain **);
+	size = (ALIGN(ndomains, 256) >> 8) * sizeof(struct dmar_domain **);
 	iommu->domains = kzalloc(size, GFP_KERNEL);
 
 	if (iommu->domains) {
@@ -1699,7 +1699,7 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
 static void free_dmar_iommu(struct intel_iommu *iommu)
 {
 	if ((iommu->domains) && (iommu->domain_ids)) {
-		int elems = (cap_ndoms(iommu->cap) >> 8) + 1;
+		int elems = ALIGN(cap_ndoms(iommu->cap), 256) >> 8;
 		int i;
 
 		for (i = 0; i < elems; i++)
-- 
1.7.9.5