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SubjectRe: [PATCH v7 5/6] iommu/arm-smmu-v3: Add support for non-strict mode
On Fri, Sep 14, 2018 at 03:30:23PM +0100, Robin Murphy wrote:
> From: Zhen Lei <thunder.leizhen@huawei.com>
>
> 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.

> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> [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.

Will

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