[PATCH] iommu: Add support to filter non-strict/lazy mode based on device names

Sai Prakash Ranjan
2020-08-25T15:43:16Z

Currently the non-strict or lazy mode of TLB invalidation can only be set
for all or no domains. This works well for development platforms where
setting to non-strict/lazy mode is fine for performance reasons but on
production devices, we need a more fine grained control to allow only
certain peripherals to support this mode where we can be sure that it is
safe. So add support to filter non-strict/lazy mode based on the device
names that are passed via cmdline parameter "iommu.nonstrict_device".

Example: iommu.nonstrict_device="7c4000.sdhci,a600000.dwc3,6048000.etr"

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
---
drivers/iommu/iommu.c | 37 +++++++++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 609bd25bf154..fd10a073f557 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -32,6 +32,9 @@ static unsigned int iommu_def_domain_type __read_mostly;
static bool iommu_dma_strict __read_mostly = true;
static u32 iommu_cmd_line __read_mostly;

+#define DEVICE_NAME_LEN 1024
+static char nonstrict_device[DEVICE_NAME_LEN] __read_mostly;
+
struct iommu_group {
struct kobject kobj;
struct kobject *devices_kobj;
@@ -327,6 +330,32 @@ static int __init iommu_dma_setup(char *str)
}
early_param("iommu.strict", iommu_dma_setup);

+static int __init iommu_nonstrict_filter_setup(char *str)
+{
+ strlcpy(nonstrict_device, str, DEVICE_NAME_LEN);
+ return 1;
+}
+__setup("iommu.nonstrict_device=", iommu_nonstrict_filter_setup);
+
+static bool iommu_nonstrict_device(struct device *dev)
+{
+ char *filter, *device;
+
+ if (!dev)
+ return false;
+
+ filter = kstrdup(nonstrict_device, GFP_KERNEL);
+ if (!filter)
+ return false;
+
+ while ((device = strsep(&filter, ","))) {
+ if (!strcmp(device, dev_name(dev)))
+ return true;
+ }
+
+ return false;
+}
+
static ssize_t iommu_group_attr_show(struct kobject *kobj,
struct attribute *__attr, char *buf)
{
@@ -1470,7 +1499,7 @@ static int iommu_get_def_domain_type(struct device *dev)

static int iommu_group_alloc_default_domain(struct bus_type *bus,
struct iommu_group *group,
- unsigned int type)
+ unsigned int type, struct device *dev)
{
struct iommu_domain *dom;

@@ -1489,7 +1518,7 @@ static int iommu_group_alloc_default_domain(struct bus_type *bus,
if (!group->domain)
group->domain = dom;

- if (!iommu_dma_strict) {
+ if (!iommu_dma_strict || iommu_nonstrict_device(dev)) {
int attr = 1;
iommu_domain_set_attr(dom,
DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE,
@@ -1509,7 +1538,7 @@ static int iommu_alloc_default_domain(struct iommu_group *group,

type = iommu_get_def_domain_type(dev);

- return iommu_group_alloc_default_domain(dev->bus, group, type);
+ return iommu_group_alloc_default_domain(dev->bus, group, type, dev);
}

/**
@@ -1684,7 +1713,7 @@ static void probe_alloc_default_domain(struct bus_type *bus,
if (!gtype.type)
gtype.type = iommu_def_domain_type;

- iommu_group_alloc_default_domain(bus, group, gtype.type);
+ iommu_group_alloc_default_domain(bus, group, gtype.type, NULL);

}

base-commit: e46b3c0d011eab9933c183d5b47569db8e377281
--
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