Good afternoon,
On 10/04/2016 09:52 AM, Konrad Rzeszutek Wilk wrote:
On Tue, Oct 04, 2016 at 09:11:39AM -0700, Glenn Serre 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.
The reason we use iommu=pt is to support using the DPDK igb_uio driver,
which we need to do on servers that have an iommu but lack ACS.
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]
What about adding IA-64 back on?
As far as I can see, IA-64 doesn't pay any attention at all to the iommu
parameter. In arch/ia64/kernel/pci-dma.c, I see
int iommu_pass_through;
but no early_param("iommu"), other occurrence of "iommu", or reference to
iommu_pass_through.
Thanks,
--Glenn S.
+ nopt [x86]
Or here?
nobypass [PPC/POWERNV]
Disable IOMMU bypass, using IOMMU for PCI devices.
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -845,6 +845,13 @@
def_bool y
depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
+config IOMMU_DEFAULT_PT
+ def_bool n
+ prompt "Set iommu=pt by default"
+ help
+ Selecting this option 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 = IS_ENABLED(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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