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authorJoerg Roedel <joerg.roedel@amd.com>2009-09-01 16:00:35 +0200
committerJoerg Roedel <joerg.roedel@amd.com>2009-09-03 16:13:46 +0200
commitac0101d396fee24994632f71b55b9f7f9ee16eff (patch)
treec38a60f42c52a230d035db00e67b3968332cc520 /arch/x86/kernel/pci-dma.c
parent37d0892c5a94e208cf863e3b7bac014edee4346d (diff)
x86/dma: Mark iommu_pass_through as __read_mostly
This variable is read most of the time. This patch marks it as such. It also documents the meaning the this variable while at it. Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Diffstat (limited to 'arch/x86/kernel/pci-dma.c')
-rw-r--r--arch/x86/kernel/pci-dma.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 1a041bcf506b..873aa079d166 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -32,7 +32,14 @@ int no_iommu __read_mostly;
/* Set this to 1 if there is a HW IOMMU in the system */
int iommu_detected __read_mostly = 0;
-int iommu_pass_through;
+/*
+ * This variable becomes 1 if iommu=pt is passed on the kernel command line.
+ * If this variable is 1, IOMMU implementations do no DMA ranslation for
+ * devices and allow every device to access to whole physical memory. This is
+ * useful if a user want to use an IOMMU only for KVM device assignment to
+ * guests and not for driver dma translation.
+ */
+int iommu_pass_through __read_mostly;
dma_addr_t bad_dma_address __read_mostly = 0;
EXPORT_SYMBOL(bad_dma_address);