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

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

[Will Deacon]

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@codeaurora.org>
> ---
>  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.

>  			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

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Re: [PATCHv9 2/8] iommu/arm-smmu: Add domain attribute for pagetable configuration

[Will Deacon]

On Mon, Nov 23, 2020 at 10:35:55PM +0530, Sai Prakash Ranjan wrote:
> Add iommu domain attribute for pagetable configuration which
> initially will be used to set quirks like for system cache aka
> last level cache to be used by client drivers like GPU to set
> right attributes for caching the hardware pagetables into the
> system cache and later can be extended to include other page
> table configuration data.
> 
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu.c | 20 ++++++++++++++++++++
>  drivers/iommu/arm/arm-smmu/arm-smmu.h |  1 +
>  include/linux/io-pgtable.h            |  4 ++++
>  include/linux/iommu.h                 |  1 +
>  4 files changed, 26 insertions(+)

Given that we're heading for a v10 to address my comments on patch 3,
then I guess you may as well split this into two patches so that I can
share just the atttibute with Rob rather than the driver parts.

Please keep it all as one series though, with the common parts at the
beginning, and I'll figure it out.

Will

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