linux-kernel - Re: [PATCH v3 09/17] iommufd: Add IOMMU_HWPT

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Date:   Fri, 28 Jul 2023 15:02:43 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Yi Liu <yi.l.liu@...el.com>
Cc:     joro@...tes.org, alex.williamson@...hat.com, kevin.tian@...el.com,
        robin.murphy@....com, baolu.lu@...ux.intel.com, cohuck@...hat.com,
        eric.auger@...hat.com, nicolinc@...dia.com, kvm@...r.kernel.org,
        mjrosato@...ux.ibm.com, chao.p.peng@...ux.intel.com,
        yi.y.sun@...ux.intel.com, peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        zhenzhong.duan@...el.com
Subject: Re: [PATCH v3 09/17] iommufd: Add IOMMU_HWPT_INVALIDATE

On Mon, Jul 24, 2023 at 04:03:58AM -0700, Yi Liu wrote:
> In nested translation, the stage-1 page table is user-managed and used by
> IOMMU hardware, so update of any present page table entry in the stage-1
> page table should be followed with an IOTLB invalidation.
> 
> This adds IOMMU_HWPT_INVALIDATE for stage-1 IOTLB invalidation.
> 
> Co-developed-by: Nicolin Chen <nicolinc@...dia.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> Signed-off-by: Yi Liu <yi.l.liu@...el.com>
> ---
>  drivers/iommu/iommufd/hw_pagetable.c    | 45 +++++++++++++++++++++++++
>  drivers/iommu/iommufd/iommufd_private.h |  9 +++++
>  drivers/iommu/iommufd/main.c            |  3 ++
>  include/uapi/linux/iommufd.h            | 22 ++++++++++++
>  4 files changed, 79 insertions(+)
> 
> diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
> index 97e4114226de..9064e6d181b4 100644
> --- a/drivers/iommu/iommufd/hw_pagetable.c
> +++ b/drivers/iommu/iommufd/hw_pagetable.c
> @@ -286,3 +286,48 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
>  	iommufd_put_object(&idev->obj);
>  	return rc;
>  }
> +
> +int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd)
> +{
> +	struct iommu_hwpt_invalidate *cmd = ucmd->cmd;
> +	struct iommufd_hw_pagetable *hwpt;
> +	u32 user_data_len, klen;
> +	u64 user_ptr;
> +	int rc = 0;
> +
> +	if (!cmd->data_len || cmd->__reserved)
> +		return -EOPNOTSUPP;
> +
> +	hwpt = iommufd_get_hwpt(ucmd, cmd->hwpt_id);
> +	if (IS_ERR(hwpt))
> +		return PTR_ERR(hwpt);
> +
> +	/* Do not allow any kernel-managed hw_pagetable */
> +	if (!hwpt->parent) {

I don't think this is needed because:

> +		rc = -EINVAL;
> +		goto out_put_hwpt;
> +	}
> +
> +	klen = hwpt->domain->ops->cache_invalidate_user_data_len;
> +	if (!hwpt->domain->ops->cache_invalidate_user || !klen) {
> +		rc = -EOPNOTSUPP;

We need to get to a place where the drivers are providing proper ops
for the domains, so this op should never exist for a paging domain.

And return EINVAL here instead.

> +		goto out_put_hwpt;
> +	}
> +
> +	/*
> +	 * Copy the needed fields before reusing the ucmd buffer, this
> +	 * avoids memory allocation in this path.
> +	 */
> +	user_ptr = cmd->data_uptr;
> +	user_data_len = cmd->data_len;

Uhh, who checks that klen < the temporary stack struct?

Jason