From fccb4e3b8ab0957628abec82675691c72f67003e Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 5 Jan 2017 18:38:26 +0000 Subject: iommu: Allow default domain type to be set on the kernel command line The IOMMU core currently initialises the default domain for each group to IOMMU_DOMAIN_DMA, under the assumption that devices will use IOMMU-backed DMA ops by default. However, in some cases it is desirable for the DMA ops to bypass the IOMMU for performance reasons, reserving use of translation for subsystems such as VFIO that require it for enforcing device isolation. Rather than modify each IOMMU driver to provide different semantics for DMA domains, instead we introduce a command line parameter that can be used to change the type of the default domain. Passthrough can then be specified using "iommu.passthrough=1" on the kernel command line. Signed-off-by: Will Deacon --- Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2ba45caabada..187ac5bc8b40 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1644,6 +1644,12 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. + iommu.passthrough= + [ARM64] Configure DMA to bypass the IOMMU by default. + Format: { "0" | "1" } + 0 - Use IOMMU translation for DMA. + 1 - Bypass the IOMMU for DMA. + unset - Use IOMMU translation for DMA. io7= [HW] IO7 for Marvel based alpha systems See comment before marvel_specify_io7 in -- cgit v1.2.3