Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE

[Baolu Lu <baolu.lu@linux.intel.com>]

On 11/17/23 9:07 PM, Yi Liu wrote:
> In nested translation, the stage-1 page table is user-managed but cached
> by the IOMMU hardware, so an update on present page table entries in the
> stage-1 page table should be followed with a cache invalidation.
> 
> Add an IOMMU_HWPT_INVALIDATE ioctl to support such a cache invalidation.
> It takes hwpt_id to specify the iommu_domain, and a multi-entry array to
> support multiple invalidation requests in one ioctl.
> 
> Check cache_invalidate_user op in the iommufd_hw_pagetable_alloc_nested,
> since all nested domains need that.
> 
> Co-developed-by: Nicolin Chen<nicolinc@nvidia.com>
> Signed-off-by: Nicolin Chen<nicolinc@nvidia.com>
> Signed-off-by: Yi Liu<yi.l.liu@intel.com>
> ---
>   drivers/iommu/iommufd/hw_pagetable.c    | 35 +++++++++++++++++++++++++
>   drivers/iommu/iommufd/iommufd_private.h |  9 +++++++
>   drivers/iommu/iommufd/main.c            |  3 +++
>   include/uapi/linux/iommufd.h            | 35 +++++++++++++++++++++++++
>   4 files changed, 82 insertions(+)
> 
> diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
> index 2abbeafdbd22..367459d92f69 100644
> --- a/drivers/iommu/iommufd/hw_pagetable.c
> +++ b/drivers/iommu/iommufd/hw_pagetable.c
> @@ -238,6 +238,11 @@ iommufd_hwpt_nested_alloc(struct iommufd_ctx *ictx,
>   		rc = -EINVAL;
>   		goto out_abort;
>   	}
> +	/* Driver is buggy by missing cache_invalidate_user in domain_ops */
> +	if (WARN_ON_ONCE(!hwpt->domain->ops->cache_invalidate_user)) {
> +		rc = -EINVAL;
> +		goto out_abort;
> +	}
>   	return hwpt_nested;

The WARN message here may cause kernel regression when users bisect
issues. Till this patch, there are no drivers support the
cache_invalidation_user callback yet.

Best regards,
baolu