> From: Jason Gunthorpe
> Sent: Wednesday, May 11, 2022 12:55 AM
>
> This control causes the ARM SMMU drivers to choose a stage 2
> implementation for the IO pagetable (vs the stage 1 usual default),
> however this choice has no visible impact to the VFIO user. Further qemu
> never implemented this and no other userspace user is known.
>
> The original description in commit f5c9ecebaf2a ("vfio/iommu_type1: add
> new VFIO_TYPE1_NESTING_IOMMU IOMMU type") suggested this was to
> "provide
> SMMU translation services to the guest operating system" however the rest
> of the API to set the guest table pointer for the stage 1 was never
> completed, or at least never upstreamed, rendering this part useless dead
> code.
>
> Since the current patches to enable nested translation, aka userspace page
> tables, rely on iommufd and will not use the enable_nesting()
> iommu_domain_op, remove this infrastructure. However, don't cut too deep
> into the SMMU drivers for now expecting the iommufd work to pick it up -
> we still need to create S2 IO page tables.
>
> Remove VFIO_TYPE1_NESTING_IOMMU and everything under it including the
> enable_nesting iommu_domain_op.
>
> Just in-case there is some userspace using this continue to treat
> requesting it as a NOP, but do not advertise support any more.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ----------------
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 16 ----------------
> drivers/iommu/iommu.c | 10 ----------
> drivers/vfio/vfio_iommu_type1.c | 12 +-----------
> include/linux/iommu.h | 3 ---
> include/uapi/linux/vfio.h | 2 +-
> 6 files changed, 2 insertions(+), 57 deletions(-)
>
> It would probably make sense for this to go through the VFIO tree with
> Robin's
> ack for the SMMU changes.
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 627a3ed5ee8fd1..b901e8973bb4ea 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2724,21 +2724,6 @@ static struct iommu_group
> *arm_smmu_device_group(struct device *dev)
> return group;
> }
>
> -static int arm_smmu_enable_nesting(struct iommu_domain *domain)
> -{
> - struct arm_smmu_domain *smmu_domain =
> to_smmu_domain(domain);
> - int ret = 0;
> -
> - mutex_lock(&smmu_domain->init_mutex);
> - if (smmu_domain->smmu)
> - ret = -EPERM;
> - else
> - smmu_domain->stage = ARM_SMMU_DOMAIN_NESTED;
> - mutex_unlock(&smmu_domain->init_mutex);
> -
> - return ret;
> -}
> -
> static int arm_smmu_of_xlate(struct device *dev, struct of_phandle_args
> *args)
> {
> return iommu_fwspec_add_ids(dev, args->args, 1);
> @@ -2865,7 +2850,6 @@ static struct iommu_ops arm_smmu_ops = {
> .flush_iotlb_all = arm_smmu_flush_iotlb_all,
> .iotlb_sync = arm_smmu_iotlb_sync,
> .iova_to_phys = arm_smmu_iova_to_phys,
> - .enable_nesting = arm_smmu_enable_nesting,
> .free = arm_smmu_domain_free,
> }
> };
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> index 568cce590ccc13..239e6f6585b48d 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> @@ -1507,21 +1507,6 @@ static struct iommu_group
> *arm_smmu_device_group(struct device *dev)
> return group;
> }
>
> -static int arm_smmu_enable_nesting(struct iommu_domain *domain)
> -{
> - struct arm_smmu_domain *smmu_domain =
> to_smmu_domain(domain);
> - int ret = 0;
> -
> - mutex_lock(&smmu_domain->init_mutex);
> - if (smmu_domain->smmu)
> - ret = -EPERM;
> - else
> - smmu_domain->stage = ARM_SMMU_DOMAIN_NESTED;
> - mutex_unlock(&smmu_domain->init_mutex);
> -
> - return ret;
> -}
> -
> static int arm_smmu_set_pgtable_quirks(struct iommu_domain *domain,
> unsigned long quirks)
> {
> @@ -1600,7 +1585,6 @@ static struct iommu_ops arm_smmu_ops = {
> .flush_iotlb_all = arm_smmu_flush_iotlb_all,
> .iotlb_sync = arm_smmu_iotlb_sync,
> .iova_to_phys = arm_smmu_iova_to_phys,
> - .enable_nesting = arm_smmu_enable_nesting,
> .set_pgtable_quirks = arm_smmu_set_pgtable_quirks,
> .free = arm_smmu_domain_free,
> }
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 857d4c2fd1a206..f33c0d569a5d03 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2561,16 +2561,6 @@ static int __init iommu_init(void)
> }
> core_initcall(iommu_init);
>
> -int iommu_enable_nesting(struct iommu_domain *domain)
> -{
> - if (domain->type != IOMMU_DOMAIN_UNMANAGED)
> - return -EINVAL;
> - if (!domain->ops->enable_nesting)
> - return -EINVAL;
> - return domain->ops->enable_nesting(domain);
> -}
> -EXPORT_SYMBOL_GPL(iommu_enable_nesting);
> -
> int iommu_set_pgtable_quirks(struct iommu_domain *domain,
> unsigned long quirk)
> {
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index 9394aa9444c10c..ff669723b0488f 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -74,7 +74,6 @@ struct vfio_iommu {
> uint64_t num_non_pinned_groups;
> wait_queue_head_t vaddr_wait;
> bool v2;
> - bool nesting;
> bool dirty_page_tracking;
> bool container_open;
> struct list_head emulated_iommu_groups;
> @@ -2207,12 +2206,6 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> if (!domain->domain)
> goto out_free_domain;
>
> - if (iommu->nesting) {
> - ret = iommu_enable_nesting(domain->domain);
> - if (ret)
> - goto out_domain;
> - }
> -
> ret = iommu_attach_group(domain->domain, group->iommu_group);
> if (ret)
> goto out_domain;
> @@ -2546,9 +2539,7 @@ static void *vfio_iommu_type1_open(unsigned
> long arg)
> switch (arg) {
> case VFIO_TYPE1_IOMMU:
> break;
> - case VFIO_TYPE1_NESTING_IOMMU:
> - iommu->nesting = true;
> - fallthrough;
> + case __VFIO_RESERVED_TYPE1_NESTING_IOMMU:
> case VFIO_TYPE1v2_IOMMU:
> iommu->v2 = true;
> break;
> @@ -2634,7 +2625,6 @@ static int
> vfio_iommu_type1_check_extension(struct vfio_iommu *iommu,
> switch (arg) {
> case VFIO_TYPE1_IOMMU:
> case VFIO_TYPE1v2_IOMMU:
> - case VFIO_TYPE1_NESTING_IOMMU:
> case VFIO_UNMAP_ALL:
> case VFIO_UPDATE_VADDR:
> return 1;
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 9208eca4b0d1ac..51cb4d3eb0d391 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -272,7 +272,6 @@ struct iommu_ops {
> * @iotlb_sync: Flush all queued ranges from the hardware TLBs and empty
> flush
> * queue
> * @iova_to_phys: translate iova to physical address
> - * @enable_nesting: Enable nesting
> * @set_pgtable_quirks: Set io page table quirks (IO_PGTABLE_QUIRK_*)
> * @free: Release the domain after use.
> */
> @@ -300,7 +299,6 @@ struct iommu_domain_ops {
> phys_addr_t (*iova_to_phys)(struct iommu_domain *domain,
> dma_addr_t iova);
>
> - int (*enable_nesting)(struct iommu_domain *domain);
> int (*set_pgtable_quirks)(struct iommu_domain *domain,
> unsigned long quirks);
>
> @@ -496,7 +494,6 @@ extern int iommu_page_response(struct device *dev,
> extern int iommu_group_id(struct iommu_group *group);
> extern struct iommu_domain *iommu_group_default_domain(struct
> iommu_group *);
>
> -int iommu_enable_nesting(struct iommu_domain *domain);
> int iommu_set_pgtable_quirks(struct iommu_domain *domain,
> unsigned long quirks);
>
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index fea86061b44e65..6e0640f0a4cad7 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -35,7 +35,7 @@
> #define VFIO_EEH 5
>
> /* Two-stage IOMMU */
> -#define VFIO_TYPE1_NESTING_IOMMU 6 /* Implies v2 */
> +#define __VFIO_RESERVED_TYPE1_NESTING_IOMMU 6 /* Implies v2
> */
>
> #define VFIO_SPAPR_TCE_v2_IOMMU 7
>
>
> base-commit: c5eb0a61238dd6faf37f58c9ce61c9980aaffd7a
> --
> 2.36.0
>
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