[PATCH v7 5/6] iommu/arm-smmu-v3: Add support for non-strict mode

On 2018-09-18 6:10 PM, Will Deacon wrote:

On Fri, Sep 14, 2018 at 03:30:23PM +0100, Robin Murphy wrote:

quoted

From: Zhen Lei <redacted>

Dynamically choose strict or non-strict mode for page table config based
on the iommu domain type.

It's the domain type in conjunction with the attribute that determines
whether we use lazy or strict invalidation.

quoted

Signed-off-by: Zhen Lei <redacted>
[rm: convert to domain attribute]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
  drivers/iommu/arm-smmu-v3.c | 30 ++++++++++++++++++++++++------
  1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index f10c852479fc..7bbfa5f7ce8e 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c

@@ -612,6 +612,7 @@ struct arm_smmu_domain {
  	struct mutex			init_mutex; /* Protects smmu pointer */
  
  	struct io_pgtable_ops		*pgtbl_ops;
+	bool				non_strict;
  
  	enum arm_smmu_domain_stage	stage;
  	union {

@@ -1633,6 +1634,9 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain)
  	if (smmu->features & ARM_SMMU_FEAT_COHERENCY)
  		pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_NO_DMA;
  
+	if (smmu_domain->non_strict)
+		pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
+
  	pgtbl_ops = alloc_io_pgtable_ops(fmt, &pgtbl_cfg, smmu_domain);
  	if (!pgtbl_ops)
  		return -ENOMEM;

@@ -1934,13 +1938,17 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
  {
  	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
  
-	if (domain->type != IOMMU_DOMAIN_UNMANAGED)
-		return -EINVAL;
-
  	switch (attr) {
  	case DOMAIN_ATTR_NESTING:
+		if (domain->type != IOMMU_DOMAIN_UNMANAGED)
+			return -EINVAL;
  		*(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
  		return 0;
+	case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
+		if (domain->type != IOMMU_DOMAIN_DMA)
+			return -EINVAL;
+		*(int *)data = smmu_domain->non_strict;
+		return 0;
  	default:
  		return -ENODEV;

Hmm, there's a change in behaviour here (and also in the set function)
which is that unknown attributes now return -ENODEV for managed domains
instead of -EINVAL. I don't know if that's a problem, but I'd be inclined
to switch on the domain type and then have a nested switch for the supported
attributes.

Sure, a nested switch did actually cross my mind, but I was worried it 
might be a little boilerplate-heavy since there's still only one of each 
case (and this quick'n'dirty copy-paste job didn't need any thought...)

If that's your preference too, though, I'll respin both driver patches 
that way.

Robin.