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

[Sai Prakash Ranjan]

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.ran...@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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