[RFC PATCH 5/6] iommu/arm-smmu: Option to treat instruction fetch as data read for SMMUv2

[Anup Patel <anup.patel-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>]

Currently, the SMMU driver by default provides unprivilege read-write
permission in page table entries of stage1 page table. For SMMUv2 with
aarch64 long descriptor format, a privilege instruction fetch will
generate context fault. To allow privilege instruction fetch from a
MMU master we need to treat instruction fetch as data read.

This patch adds an optional DT attribute 'smmu-inst-as-data' to treat
privilege/unprivilege instruction fetch as data read for SMMUv2.

Signed-off-by: Anup Patel <anup.patel-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
Reviewed-by: Ray Jui <rjui-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
Reviewed-by: Vikram Prakash <vikramp-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
Reviewed-by: Scott Branden <sbranden-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
---
 drivers/iommu/arm-smmu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 43424fe..a14850b 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -169,6 +169,9 @@
 #define S2CR_TYPE_TRANS			(0 << S2CR_TYPE_SHIFT)
 #define S2CR_TYPE_BYPASS		(1 << S2CR_TYPE_SHIFT)
 #define S2CR_TYPE_FAULT			(2 << S2CR_TYPE_SHIFT)
+#define S2CR_INSTCFG_SHIFT		26
+#define S2CR_INSTCFG_MASK		0x3
+#define S2CR_INSTCFG_DATA		(0x2 << S2CR_INSTCFG_SHIFT)
 
 /* Context bank attribute registers */
 #define ARM_SMMU_GR1_CBAR(n)		(0x0 + ((n) << 2))
@@ -305,6 +308,7 @@ struct arm_smmu_device {
 	u32				features;
 
 #define ARM_SMMU_OPT_SECURE_CFG_ACCESS (1 << 0)
+#define ARM_SMMU_OPT_INST_AS_DATA      (1 << 1)
 	u32				options;
 	enum arm_smmu_arch_version	version;
 
@@ -366,6 +370,7 @@ struct arm_smmu_option_prop {
 
 static struct arm_smmu_option_prop arm_smmu_options[] = {
 	{ ARM_SMMU_OPT_SECURE_CFG_ACCESS, "calxeda,smmu-secure-config-access" },
+	{ ARM_SMMU_OPT_INST_AS_DATA, "smmu-inst-as-data" },
 	{ 0, NULL},
 };
 
@@ -1097,6 +1102,9 @@ static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain,
 		idx = cfg->smrs ? cfg->smrs[i].idx : cfg->streamids[i];
 		s2cr = S2CR_TYPE_TRANS |
 		       (smmu_domain->cfg.cbndx << S2CR_CBNDX_SHIFT);
+		if ((smmu->version == ARM_SMMU_V2) &&
+		    (smmu->options & ARM_SMMU_OPT_INST_AS_DATA))
+			s2cr |= S2CR_INSTCFG_DATA;
 		writel_relaxed(s2cr, gr0_base + ARM_SMMU_GR0_S2CR(idx));
 	}
 
-- 
1.9.1