Good morning,
On 09/29/2016 11:11 AM, Konrad Rzeszutek Wilk wrote:
On Thu, Sep 29, 2016 at 09:58:55AM -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.
What's the reason / use-case for it?
The top-level reason is we would prefer our kernel command line to not
grow any larger than it already is.
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.
Thanks,
--Glenn S.
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"
+ 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);
_______________________________________________
iommu mailing list
[email protected]
https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.linuxfoundation.org_mailman_listinfo_iommu&d=DQIBAg&c=IL_XqQWOjubgfqINi2jTzg&r=3biwyMBB1JD9rm0R5wqz7zcDVkNif9HJ5Pflrr18dkw&m=JAPHQW96EkN4p33Jc7yZG15XGwK_KprKNxbbQvkgJ1c&s=HSZCSWNkVn-60uhbA_07tZgukoQbP3zZAhU0con30VY&e=
_______________________________________________
iommu mailing list
[email protected]
https://lists.linuxfoundation.org/mailman/listinfo/iommu
