From ac0101d396fee24994632f71b55b9f7f9ee16eff Mon Sep 17 00:00:00 2001 From: Joerg Roedel <joerg.roedel@amd.com> Date: Tue, 1 Sep 2009 16:00:35 +0200 Subject: [PATCH] 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> --- arch/x86/kernel/pci-dma.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) 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); -- 2.30.9