From: Olof Johansson <olof@lixom.net>
Date: Fri, 20 Jul 2018 11:02:23 -0700
Subject: iommu: Add config option to set passthrough as default
Git-commit: 58d1131777a4b7c228267b809bd88f7be66edcfb
Patch-mainline: v4.19-rc1
References: fate#326981
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>
---
Documentation/admin-guide/kernel-parameters.txt | 3 ++-
arch/x86/kernel/pci-dma.c | 8 ++++++++
drivers/iommu/Kconfig | 11 +++++++++++
drivers/iommu/iommu.c | 4 ++++
4 files changed, 25 insertions(+), 1 deletion(-)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1659,7 +1659,8 @@
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/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -42,8 +42,14 @@ 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[];
@@ -200,6 +206,8 @@ 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);
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
endmenu
+config IOMMU_DEFAULT_PASSTHROUGH
+ bool "IOMMU passthrough by default"
+ depends on IOMMU_API
+ help
+ Enable passthrough by default, removing the need to pass in
+ iommu.passthrough=on or iommu=pt through command line. If this
+ is enabled, you can still disable with iommu.passthrough=off
+ or iommu=nopt depending on the architecture.
+
+ If unsure, say N here.
+
config IOMMU_IOVA
tristate
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -36,7 +36,11 @@
static struct kset *iommu_group_kset;
static DEFINE_IDA(iommu_group_ida);
+#ifdef CONFIG_IOMMU_DEFAULT_PASSTHROUGH
+static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY;
+#else
static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;
+#endif
struct iommu_callback_data {
const struct iommu_ops *ops;