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authorWill Deacon <will.deacon@arm.com>2017-01-05 18:38:26 +0000
committerWill Deacon <will.deacon@arm.com>2017-04-06 16:06:44 +0100
commitfccb4e3b8ab0957628abec82675691c72f67003e (patch)
tree7671e81a6d9fce8266a49d6e397917dd317a0eab /drivers/iommu
parentbeb3c6a066bff1ba412f983cb9d1a42f4cd8f76a (diff)
downloadlinux-fccb4e3b8ab0957628abec82675691c72f67003e.tar.bz2
iommu: Allow default domain type to be set on the kernel command line
The IOMMU core currently initialises the default domain for each group to IOMMU_DOMAIN_DMA, under the assumption that devices will use IOMMU-backed DMA ops by default. However, in some cases it is desirable for the DMA ops to bypass the IOMMU for performance reasons, reserving use of translation for subsystems such as VFIO that require it for enforcing device isolation. Rather than modify each IOMMU driver to provide different semantics for DMA domains, instead we introduce a command line parameter that can be used to change the type of the default domain. Passthrough can then be specified using "iommu.passthrough=1" on the kernel command line. Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'drivers/iommu')
-rw-r--r--drivers/iommu/iommu.c28
1 files changed, 25 insertions, 3 deletions
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3b67144dead2..770ba7e7ef4d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -36,6 +36,7 @@
static struct kset *iommu_group_kset;
static DEFINE_IDA(iommu_group_ida);
+static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;
struct iommu_callback_data {
const struct iommu_ops *ops;
@@ -112,6 +113,18 @@ static int __iommu_attach_group(struct iommu_domain *domain,
static void __iommu_detach_group(struct iommu_domain *domain,
struct iommu_group *group);
+static int __init iommu_set_def_domain_type(char *str)
+{
+ bool pt;
+
+ if (!str || strtobool(str, &pt))
+ return -EINVAL;
+
+ iommu_def_domain_type = pt ? IOMMU_DOMAIN_IDENTITY : IOMMU_DOMAIN_DMA;
+ return 0;
+}
+early_param("iommu.passthrough", iommu_set_def_domain_type);
+
static ssize_t iommu_group_attr_show(struct kobject *kobj,
struct attribute *__attr, char *buf)
{
@@ -1015,10 +1028,19 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev)
* IOMMU driver.
*/
if (!group->default_domain) {
- group->default_domain = __iommu_domain_alloc(dev->bus,
- IOMMU_DOMAIN_DMA);
+ struct iommu_domain *dom;
+
+ dom = __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
+ if (!dom && iommu_def_domain_type != IOMMU_DOMAIN_DMA) {
+ dev_warn(dev,
+ "failed to allocate default IOMMU domain of type %u; falling back to IOMMU_DOMAIN_DMA",
+ iommu_def_domain_type);
+ dom = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_DMA);
+ }
+
+ group->default_domain = dom;
if (!group->domain)
- group->domain = group->default_domain;
+ group->domain = dom;
}
ret = iommu_group_add_device(group, dev);