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iommu: Add config option to set passthrough as default

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This allows the default behavior to be controlled by a kernel config
option instead of changing the commandline for the kernel to include
"iommu.passthrough=on" or "iommu=pt" on machines where this is desired.

Likewise, for machines where this config option is enabled, it can be
disabled at boot time with "iommu.passthrough=off" or "iommu=nopt".

Also corrected iommu=pt documentation for IA-64, since it has no code that
parses iommu= at all.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Olof Johansson
2018-07-20 11:02:23 -07:00
committed by Joerg Roedel
parent c52c72d3de
commit 58d1131777
4 changed files with 25 additions and 1 deletions
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8
arch/x86/kernel/pci-dma.c
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@@ -40,8 +40,14 @@ int iommu_detected __read_mostly = 0;
* devices and allow every device to access to whole physical memory. This is
* useful if a user wants to use an IOMMU only for KVM device assignment to
* guests and not for driver dma translation.
* It is also possible to disable by default in kernel config, and enable with
* iommu=nopt at boot time.
*/
#ifdef CONFIG_IOMMU_DEFAULT_PASSTHROUGH
int iommu_pass_through __read_mostly = 1;
#else
int iommu_pass_through __read_mostly;
#endif
extern struct iommu_table_entry __iommu_table[], __iommu_table_end[];
@@ -135,6 +141,8 @@ static __init int iommu_setup(char *p)
#endif
if (!strncmp(p, "pt", 2))
iommu_pass_through = 1;
if (!strncmp(p, "nopt", 4))
iommu_pass_through = 0;
gart_parse_options(p);