Re: [PATCH v5 5/8] iommu/arm-smmu-v3: Add bypass flag to arm_smmu_write_strtab_ent()

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On 2021-05-24 12:02, Shameer Kolothum wrote:
By default, disable_bypass is set and any dev without an iommu domain
installs STE with CFG_ABORT during arm_smmu_init_bypass_stes(). Introduce
a "bypass" flag to arm_smmu_write_strtab_ent() so that we can force it to
install CFG_BYPASS STE for specific SIDs. This will be useful in follow
up patch to install bypass for IORT RMR SIDs.

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
---
  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 754bad6092c1..f9195b740f48 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1174,7 +1174,7 @@ static void arm_smmu_sync_ste_for_sid(struct arm_smmu_device *smmu, u32 sid)
  }
static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
-				      __le64 *dst)
+				      __le64 *dst, bool bypass)
  {
  	/*
  	 * This is hideously complicated, but we only really care about
@@ -1245,7 +1245,7 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
/* Bypass/fault */
  	if (!smmu_domain || !(s1_cfg || s2_cfg)) {
-		if (!smmu_domain && disable_bypass)
+		if (!smmu_domain && disable_bypass && !bypass)

Umm...

  			val |= FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_ABORT);
  		else
  			val |= FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_BYPASS);
@@ -1320,7 +1320,7 @@ static void arm_smmu_init_bypass_stes(__le64 *strtab, unsigned int nent)
  	unsigned int i;
for (i = 0; i < nent; ++i) {
-		arm_smmu_write_strtab_ent(NULL, -1, strtab);
+		arm_smmu_write_strtab_ent(NULL, -1, strtab, false);

...and in particular, an operation named "init_bypass_stes" passing bypass=false is just breaking my brain. Can we pull the logic for default bypass/fault out to here as part of the refactoring so that it actually makes sense?

Robin.

  		strtab += STRTAB_STE_DWORDS;
  	}
  }
@@ -2097,7 +2097,7 @@ static void arm_smmu_install_ste_for_dev(struct arm_smmu_master *master)
  		if (j < i)
  			continue;
- arm_smmu_write_strtab_ent(master, sid, step);
+		arm_smmu_write_strtab_ent(master, sid, step, false);
  	}
  }



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