RE: [PATCH 06/12] iommufd: IOMMU_HWPT_ALLOC allocation with user data

[Liu, Yi L]

> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, March 10, 2023 11:02 AM
> 
> On 3/9/23 4:09 PM, Yi Liu wrote:
> > IOMMU_HWPT_ALLOC already supports iommu_domain allocation for
> usersapce.
> > But it can only allocate hw_pagetables linked with IOAS. There are needs
> > to support hw_pagetable allocation with parameters specified by user. For
> > example, in nested translation, user needs to allocate hw_pagetable for
> > the stage-1 translation (e.g. a single I/O page table or a set of I/O page
> > tables) with user data. It also needs provide a stage-2 hw_pagetable
> which
> > is linked to the GPA IOAS.
> >
> > This extends IOMMU_HWPT_ALLOC to accept user specified parameter
> and hwpt
> > ID in @pt_id field. Such as the user-managed stage-1 hwpt, which requires
> > a parent hwpt to point to stage-2 translation.
> >
> > enum iommu_hwpt_type is defined to differentiate the user parameters
> use
> > by different usages. For the allocations that don't require user parameter,
> > IOMMU_HWPT_TYPE_DEFAULT is defined for backward compatibility.
> Other types
> > would be added by future iommu vendor driver extensions.
> >
> > Co-developed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > ---
> >   drivers/iommu/iommufd/hw_pagetable.c | 94
> +++++++++++++++++++++++++---
> >   drivers/iommu/iommufd/main.c         |  2 +-
> >   include/uapi/linux/iommufd.h         | 30 +++++++++
> >   3 files changed, 115 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/iommu/iommufd/hw_pagetable.c
> b/drivers/iommu/iommufd/hw_pagetable.c
> > index 6e45ec0a66fa..64e7cf7142e1 100644
> > --- a/drivers/iommu/iommufd/hw_pagetable.c
> > +++ b/drivers/iommu/iommufd/hw_pagetable.c
> > @@ -165,34 +165,106 @@ iommufd_hw_pagetable_alloc(struct
> iommufd_ctx *ictx, struct iommufd_ioas *ioas,
> >   	return ERR_PTR(rc);
> >   }
> >
> > +/*
> > + * size of page table type specific data, indexed by
> > + * enum iommu_hwpt_type.
> > + */
> > +static const size_t iommufd_hwpt_alloc_data_size[] = {
> > +	[IOMMU_HWPT_TYPE_DEFAULT] = 0,
> > +};
> > +
> >   int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
> >   {
> >   	struct iommu_hwpt_alloc *cmd = ucmd->cmd;
> > -	struct iommufd_hw_pagetable *hwpt;
> > +	struct iommufd_hw_pagetable *hwpt, *parent = NULL;
> > +	struct iommufd_object *pt_obj;
> >   	struct iommufd_device *idev;
> >   	struct iommufd_ioas *ioas;
> > +	const struct iommu_ops *ops;
> > +	void *data = NULL;
> > +	u32 klen;
> >   	int rc;
> 
> Reverse Christmas tree format. Ditto to other places in this file.

Got it.

> >
> > -	if (cmd->flags)
> > +	if (cmd->__reserved || cmd->flags)
> >   		return -EOPNOTSUPP;
> >
> >   	idev = iommufd_get_device(ucmd, cmd->dev_id);
> >   	if (IS_ERR(idev))
> >   		return PTR_ERR(idev);
> >
> > -	ioas = iommufd_get_ioas(ucmd, cmd->pt_id);
> > -	if (IS_ERR(ioas)) {
> > -		rc = PTR_ERR(ioas);
> > +	ops = dev_iommu_ops(idev->dev);
> > +	if (!ops) {
> > +		rc = -EOPNOTSUPP;
> >   		goto out_put_idev;
> >   	}
> 
> No need to check. dev_iommu_ops() will never returns a NULL.

Got it.

> >
> > +	/* Only support IOMMU_HWPT_TYPE_DEFAULT for now */
> > +	if (cmd->data_type != IOMMU_HWPT_TYPE_DEFAULT) {
> > +		rc = -EINVAL;
> > +		goto out_put_idev;
> > +	}
> > +
> > +	pt_obj = iommufd_get_object(ucmd->ictx, cmd->pt_id,
> IOMMUFD_OBJ_ANY);
> > +	if (IS_ERR(pt_obj)) {
> > +		rc = -EINVAL;
> > +		goto out_put_idev;
> > +	}
> > +
> > +	switch (pt_obj->type) {
> > +	case IOMMUFD_OBJ_IOAS:
> > +		ioas = container_of(pt_obj, struct iommufd_ioas, obj);
> > +		break;
> > +	case IOMMUFD_OBJ_HW_PAGETABLE:
> > +		/* pt_id points HWPT only when data_type
> is !IOMMU_HWPT_TYPE_DEFAULT */
> > +		if (cmd->data_type == IOMMU_HWPT_TYPE_DEFAULT) {
> > +			rc = -EINVAL;
> > +			goto out_put_pt;
> > +		}
> > +
> > +		parent = container_of(pt_obj, struct
> iommufd_hw_pagetable, obj);
> > +		/*
> > +		 * Cannot allocate user-managed hwpt linking to
> auto_created
> > +		 * hwpt. If the parent hwpt is already a user-managed hwpt,
> > +		 * don't allocate another user-managed hwpt linking to it.
> > +		 */
> > +		if (parent->auto_domain || parent->parent) {
> > +			rc = -EINVAL;
> > +			goto out_put_pt;
> > +		}
> > +		ioas = parent->ioas;
> > +		break;
> > +	default:
> > +		rc = -EINVAL;
> > +		goto out_put_pt;
> > +	}
> > +
> > +	klen = iommufd_hwpt_alloc_data_size[cmd->data_type];
> > +	if (klen) {
> > +		if (!cmd->data_len) {
> > +			rc = -EINVAL;
> > +			goto out_put_pt;
> > +		}
> 
> Is the user_data still valid if (cmd->data_len < klen)?

Yes, one day if kernel has new fields added in the end of the uapi
structure but qemu is using an old uapi header. In such case, the
extra byte should be zeroed.

> 
> > +
> > +		data = kzalloc(klen, GFP_KERNEL);
> > +		if (!data) {
> > +			rc = -ENOMEM;
> > +			goto out_put_pt;
> > +		}
> > +
> > +		rc = copy_struct_from_user(data, klen,
> > +					   u64_to_user_ptr(cmd->data_uptr),
> > +					   cmd->data_len);
> > +		if (rc)
> > +			goto out_free_data;
> > +	}
> > +
> >   	mutex_lock(&ioas->mutex);
> >   	hwpt = iommufd_hw_pagetable_alloc(ucmd->ictx, ioas, idev,
> > -					  NULL, NULL, false);
> > +					  parent, data, false);
> >   	mutex_unlock(&ioas->mutex);
> >   	if (IS_ERR(hwpt)) {
> >   		rc = PTR_ERR(hwpt);
> > -		goto out_put_ioas;
> > +		goto out_free_data;
> >   	}
> >
> >   	cmd->out_hwpt_id = hwpt->obj.id;
> > @@ -200,12 +272,14 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd
> *ucmd)
> >   	if (rc)
> >   		goto out_hwpt;
> >   	iommufd_object_finalize(ucmd->ictx, &hwpt->obj);
> > -	goto out_put_ioas;
> > +	goto out_free_data;
> >
> >   out_hwpt:
> >   	iommufd_object_abort_and_destroy(ucmd->ictx, &hwpt->obj);
> > -out_put_ioas:
> > -	iommufd_put_object(&ioas->obj);
> > +out_free_data:
> > +	kfree(data);
> > +out_put_pt:
> > +	iommufd_put_object(pt_obj);
> >   out_put_idev:
> >   	iommufd_put_object(&idev->obj);
> >   	return rc;
> > diff --git a/drivers/iommu/iommufd/main.c
> b/drivers/iommu/iommufd/main.c
> > index f079c0bda46b..7ab1e2c638a1 100644
> > --- a/drivers/iommu/iommufd/main.c
> > +++ b/drivers/iommu/iommufd/main.c
> > @@ -295,7 +295,7 @@ struct iommufd_ioctl_op {
> >   static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
> >   	IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct
> iommu_destroy, id),
> >   	IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct
> iommu_hwpt_alloc,
> > -		 __reserved),
> > +		 data_uptr),
> >   	IOCTL_OP(IOMMU_DEVICE_GET_HW_INFO,
> iommufd_device_get_hw_info,
> >   		 struct iommu_hw_info, __reserved),
> >   	IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
> > diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> > index 4ac525897b82..48781ff40a37 100644
> > --- a/include/uapi/linux/iommufd.h
> > +++ b/include/uapi/linux/iommufd.h
> > @@ -347,6 +347,14 @@ struct iommu_vfio_ioas {
> >   };
> >   #define IOMMU_VFIO_IOAS _IO(IOMMUFD_TYPE,
> IOMMUFD_CMD_VFIO_IOAS)
> >
> > +/**
> > + * enum iommu_hwpt_type - IOMMU HWPT Type
> > + * @IOMMU_HWPT_TYPE_DEFAULT: default
> > + */
> > +enum iommu_hwpt_type {
> > +	IOMMU_HWPT_TYPE_DEFAULT,
> > +};
> > +
> >   /**
> >    * struct iommu_hwpt_alloc - ioctl(IOMMU_HWPT_ALLOC)
> >    * @size: sizeof(struct iommu_hwpt_alloc)
> > @@ -355,12 +363,31 @@ struct iommu_vfio_ioas {
> >    * @pt_id: The IOAS to connect this HWPT to
> >    * @out_hwpt_id: The ID of the new HWPT
> >    * @__reserved: Must be 0
> > + * @data_type: One of enum iommu_hwpt_type
> > + * @data_len: Length of the type specific data
> > + * @data_uptr: User pointer to the type specific data
> >    *
> >    * Explicitly allocate a hardware page table object. This is the same
> object
> >    * type that is returned by iommufd_device_attach() and represents the
> >    * underlying iommu driver's iommu_domain kernel object.
> >    *
> >    * A normal HWPT will be created with the mappings from the given IOAS.
> > + * The @data_type for its allocation can be set to
> IOMMU_HWPT_TYPE_DEFAULT, or
> > + * another type (being listed below) to specialize a kernel-managed
> HWPT.
> > + *
> > + * A user-managed HWPT will be created from a given parent HWPT via
> @pt_id, in
> > + * which the parent HWPT must be allocated previously via the same ioctl
> from a
> > + * given IOAS. The @data_type must not be set to
> IOMMU_HWPT_TYPE_DEFAULT but a
> > + * pre-defined type corresponding to the underlying IOMMU hardware.
> > + *
> > + * If the @data_type is set to IOMMU_HWPT_TYPE_DEFAULT, both the
> @data_len and
> > + * the @data_uptr will be ignored. Otherwise, both of them must be
> given.
> > + *
> > + *
> +==============================+=============================
> ========+===========+
> > + * | @data_type                   |    Data structure in @data_uptr     |   @pt_id
> |
> > + * +------------------------------+-------------------------------------+-----------+
> > + * | IOMMU_HWPT_TYPE_DEFAULT      |               N/A                   |    IOAS
> |
> > + * +------------------------------+-------------------------------------+-----------+
> >    */
> >   struct iommu_hwpt_alloc {
> >   	__u32 size;
> > @@ -369,6 +396,9 @@ struct iommu_hwpt_alloc {
> >   	__u32 pt_id;
> >   	__u32 out_hwpt_id;
> >   	__u32 __reserved;
> > +	__u32 data_type;
> > +	__u32 data_len;
> > +	__aligned_u64 data_uptr;
> >   };
> >   #define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE,
> IOMMUFD_CMD_HWPT_ALLOC)
> 
> Best regards,
> baolu