Re: [PATCH v4 4/5] iommu/arm-smmu-v3: add support for non-strict mode

From: Robin Murphy
Date: Thu Aug 09 2018 - 07:06:35 EST


On 06/08/18 13:27, Zhen Lei wrote:
Dynamically choose strict or non-strict mode for page table config based
on the iommu domain type.

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
drivers/iommu/arm-smmu-v3.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 2f1304b..904bc1e 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1622,6 +1622,11 @@ 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 (domain->type == IOMMU_DOMAIN_DMA) {
+ domain->non_strict = 1;
+ pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
+ }
+
pgtbl_ops = alloc_io_pgtable_ops(fmt, &pgtbl_cfg, smmu_domain);
if (!pgtbl_ops)
return -ENOMEM;
@@ -1782,7 +1787,7 @@ static void arm_smmu_iotlb_sync(struct iommu_domain *domain)
{
struct arm_smmu_device *smmu = to_smmu_domain(domain)->smmu;

- if (smmu)
+ if (smmu && !domain->non_strict)

That doesn't smell right - even in non-strict domains we still need stuff like walk cache invalidations for non-leaf unmaps to be synchronous, so we can't just ignore all sync operations at the driver level. I think the right thing to do to elide the "normal" sync on unmap is to first convert __iommu_dma_unmap to use iommu_unmap_fast()/iommu_tlb_sync(), then make it not issue that sync at all for non-strict domains.

Robin.

__arm_smmu_tlb_sync(smmu);
}

--
1.8.3