Re: [RESEND PATCH v2 3/3] iommu/arm-smmu: Add support for DOMAIN_ATTR_SPLIT_TABLES

Robin Murphy
2019-07-10T16:45:47Z

On 08/07/2019 20:00, Jordan Crouse wrote:
> When DOMAIN_ATTR_SPLIT_TABLES is specified for pass ARM_64_LPAE_SPLIT_S1
> to io_pgtable_ops to allocate and initialize TTBR0 and TTBR1 pagetables.
>
> v3: Moved all the pagetable specific work into io-pgtable-arm
> in a previous patch.
>
> Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> ---
>
> drivers/iommu/arm-smmu.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 653b6b3..7a6b4bb 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -257,6 +257,7 @@ struct arm_smmu_domain {
> bool non_strict;
> struct mutex init_mutex; /* Protects smmu pointer */
> spinlock_t cb_lock; /* Serialises ATS1* ops and TLB syncs */
> + u32 attributes;
> struct iommu_domain domain;
> };
>
> @@ -832,7 +833,11 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> ias = smmu->va_size;
> oas = smmu->ipa_size;
> if (cfg->fmt == ARM_SMMU_CTX_FMT_AARCH64) {
> - fmt = ARM_64_LPAE_S1;
> + if (smmu_domain->attributes &
> + (1 << DOMAIN_ATTR_SPLIT_TABLES))
> + fmt = ARM_64_LPAE_SPLIT_S1;
> + else
> + fmt = ARM_64_LPAE_S1;
> } else if (cfg->fmt == ARM_SMMU_CTX_FMT_AARCH32_L) {
> fmt = ARM_32_LPAE_S1;
> ias = min(ias, 32UL);
> @@ -1582,6 +1587,10 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
> case DOMAIN_ATTR_NESTING:
> *(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
> return 0;
> + case DOMAIN_ATTR_SPLIT_TABLES:
> + *(int *)data = !!(smmu_domain->attributes &
> + (1 << DOMAIN_ATTR_SPLIT_TABLES));

I'm not really a fan of always claiming to support this but silently
ignoring it depending on hardware/kernel configuration - it seems
somewhat tricky to make callers properly robust against making false
assumptions (e.g. consider if the system is booted with
"arm-smmu.force_stage=2").

Robin.

> + return 0;
> default:
> return -ENODEV;
> }
> @@ -1622,6 +1631,11 @@ static int arm_smmu_domain_set_attr(struct iommu_domain *domain,
> else
> smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
> break;
> + case DOMAIN_ATTR_SPLIT_TABLES:
> + if (*((int *)data))
> + smmu_domain->attributes |=
> + (1 << DOMAIN_ATTR_SPLIT_TABLES);
> + break;
> default:
> ret = -ENODEV;
> }
>