Good morning,
On 09/29/2016 11:31 AM, Alex Williamson wrote:
On Thu, 29 Sep 2016 09:58:55 -0700
Glenn Serre <[email protected]> wrote:
Add CONFIG_IOMMU_DEFAULT_PT for iommu=pt
Allow default to iommu=pt without adding to command line.
Add iommu=nopt to turn off default.
Signed-off-by: Glenn Serre <[email protected]>
---
Documentation/kernel-parameters.txt | 3 ++-
arch/x86/Kconfig | 7 +++++++
arch/x86/kernel/pci-dma.c | 6 ++++++
3 files changed, 15 insertions(+), 1 deletion(-)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1607,7 +1607,8 @@
nomerge
forcesac
soft
- pt [x86, IA-64]
+ pt [x86]
+ nopt [x86]
nobypass [PPC/POWERNV]
Disable IOMMU bypass, using IOMMU for PCI devices.
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -845,6 +845,15 @@
def_bool y
depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
+config IOMMU_DEFAULT_PT
+ int "Default iommu pt value (0-1)"
+ range 0 1
+ default "0"
+ prompt "Set to 1 to default to iommu=pt"
An integer that can be either zero or one... IOW a bool. There's
support for bools in Kconfig.
We had discussion about that during in-house code review. My initial
take was bool like INTEL_IOMMU_DEFAULT_ON, but reviewers thought the
current "right" way was range 0-1 like MTRR_SANITIZER_ENABLE_DEFAULT to
avoid an ifdef, else, endif:
#ifdef CONFIG_IOMMU_DEFAULT_PT
int iommu_pass_through __read_mostly = 1;
#else
int iommu_pass_through __read_mostly;
#endif /* CONFIG_IOMMU_DEFAULT_PT */
I'll go with whatever y'all prefer.
Thanks,
--Glenn S.
+ help
+ Setting this option to 1 will set iommu passthrough (iommu=pt)
+ by default. Use iommu=nopt to override.
+
config MAXSMP
bool "Enable Maximum number of SMP Processors and NUMA Nodes"
depends on X86_64 && SMP && DEBUG_KERNEL
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -43,7 +43,7 @@
* useful if a user wants to use an IOMMU only for KVM device
assignment to
* guests and not for driver dma translation.
*/
-int iommu_pass_through __read_mostly;
+int iommu_pass_through __read_mostly = CONFIG_IOMMU_DEFAULT_PT;
extern struct iommu_table_entry __iommu_table[], __iommu_table_end[];
@@ -196,6 +196,8 @@
#endif
if (!strncmp(p, "pt", 2))
iommu_pass_through = 1;
+ if (!strncmp(p, "nopt", 4))
+ iommu_pass_through = 0;
gart_parse_options(p);
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