Re: [PATCHv9 3/8] iommu/arm-smmu: Move non-strict mode to use io_pgtable_domain_attr

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On 2020-11-25 03:09, Will Deacon wrote:
On Mon, Nov 23, 2020 at 10:35:56PM +0530, Sai Prakash Ranjan wrote:
Now that we have a struct io_pgtable_domain_attr with quirks,
use that for non_strict mode as well thereby removing the need
for more members of arm_smmu_domain in the future.

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 8 +++-----
 drivers/iommu/arm/arm-smmu/arm-smmu.h | 1 -
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 4b9b10fe50ed..f56f266ebdf7 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -786,9 +786,6 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 			goto out_clear_smmu;
 	}

-	if (smmu_domain->non_strict)
-		pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
-
 	if (smmu_domain->pgtbl_cfg.quirks)
 		pgtbl_cfg.quirks |= smmu_domain->pgtbl_cfg.quirks;

@@ -1527,7 +1524,8 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
 	case IOMMU_DOMAIN_DMA:
 		switch (attr) {
 		case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
-			*(int *)data = smmu_domain->non_strict;
+			if (smmu_domain->pgtbl_cfg.quirks & IO_PGTABLE_QUIRK_NON_STRICT)
+				*(int *)data = smmu_domain->pgtbl_cfg.quirks;

I still don't think this is right :(
We need to set *data to 1 or 0 depending on whether or not the non-strict
quirk is set, i.e:

bool non_strict = smmu_domain->pgtbl_cfg.quirks & IO_PGTABLE_QUIRK_NON_STRICT;
	*(int *)data = non_strict;

Your code above leaves *data uninitialised if non_strict is not set.

Ugh sorry, I should have looked at this some more before hurrying up
to post, will fix it.


 			return 0;
 		default:
 			return -ENODEV;
@@ -1578,7 +1576,7 @@ static int arm_smmu_domain_set_attr(struct iommu_domain *domain,
 	case IOMMU_DOMAIN_DMA:
 		switch (attr) {
 		case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
-			smmu_domain->non_strict = *(int *)data;
+			smmu_domain->pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;

And this is broken because if *data is 0, then you _set_ the quirk, which is
the opposite of what we should be doing.

In other words, although the implementation has changed, the semantics have
not.


Will fix this to have quirk set only when *data = 1 and unset in case of 0.

Thanks,
Sai

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