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

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Date:   Tue, 25 Aug 2020 21:12:49 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>
Cc:     iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Subject: [PATCH] iommu: Add support to filter non-strict/lazy mode based on device names

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@...eaurora.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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