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Date:   Thu, 7 Dec 2023 14:59:17 +0800
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Subject: Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE
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To:     <joro@8bytes.org>, <alex.williamson@redhat.com>, <jgg@nvidia.com>,
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References: <20231117130717.19875-1-yi.l.liu@intel.com>
 <20231117130717.19875-3-yi.l.liu@intel.com>
From:   Yi Liu <yi.l.liu@intel.com>
In-Reply-To: <20231117130717.19875-3-yi.l.liu@intel.com>
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On 2023/11/17 21:07, 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;
>   
>   out_abort:
> @@ -370,4 +375,34 @@ int iommufd_hwpt_get_dirty_bitmap(struct iommufd_ucmd *ucmd)
>   
>   	iommufd_put_object(&hwpt_paging->common.obj);
>   	return rc;
> +};
> +
> +int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd)
> +{
> +	struct iommu_hwpt_invalidate *cmd = ucmd->cmd;
> +	struct iommu_user_data_array data_array = {
> +		.type = cmd->req_type,
> +		.uptr = u64_to_user_ptr(cmd->reqs_uptr),
> +		.entry_len = cmd->req_len,
> +		.entry_num = cmd->req_num,
> +	};
> +	struct iommufd_hw_pagetable *hwpt;
> +	int rc = 0;
> +
> +	if (cmd->req_type == IOMMU_HWPT_DATA_NONE)
> +		return -EINVAL;
> +	if (!cmd->reqs_uptr || !cmd->req_len || !cmd->req_num)
> +		return -EINVAL;
> +
> +	hwpt = iommufd_hw_pagetable_get_nested(ucmd, cmd->hwpt_id);
> +	if (IS_ERR(hwpt))
> +		return PTR_ERR(hwpt);
> +
> +	rc = hwpt->domain->ops->cache_invalidate_user(hwpt->domain, &data_array,
> +						      &cmd->out_driver_error_code);
> +	cmd->req_num = data_array.entry_num;
> +	if (iommufd_ucmd_respond(ucmd, sizeof(*cmd)))
> +		return -EFAULT;
> +	iommufd_put_object(&hwpt->obj);
> +	return rc;
>   }
> diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> index a74cfefffbc6..160521800d9b 100644
> --- a/drivers/iommu/iommufd/iommufd_private.h
> +++ b/drivers/iommu/iommufd/iommufd_private.h
> @@ -301,6 +301,7 @@ void iommufd_hwpt_paging_abort(struct iommufd_object *obj);
>   void iommufd_hwpt_nested_destroy(struct iommufd_object *obj);
>   void iommufd_hwpt_nested_abort(struct iommufd_object *obj);
>   int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd);
> +int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd);
>   
>   static inline void iommufd_hw_pagetable_put(struct iommufd_ctx *ictx,
>   					    struct iommufd_hw_pagetable *hwpt)
> @@ -318,6 +319,14 @@ static inline void iommufd_hw_pagetable_put(struct iommufd_ctx *ictx,
>   	refcount_dec(&hwpt->obj.users);
>   }
>   
> +static inline struct iommufd_hw_pagetable *
> +iommufd_hw_pagetable_get_nested(struct iommufd_ucmd *ucmd, u32 id)
> +{
> +	return container_of(iommufd_get_object(ucmd->ictx, id,
> +					       IOMMUFD_OBJ_HWPT_NESTED),
> +			    struct iommufd_hw_pagetable, obj);
> +}
> +
>   struct iommufd_group {
>   	struct kref ref;
>   	struct mutex lock;
> diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
> index 45b9d40773b1..6edef860f91c 100644
> --- a/drivers/iommu/iommufd/main.c
> +++ b/drivers/iommu/iommufd/main.c
> @@ -309,6 +309,7 @@ union ucmd_buffer {
>   	struct iommu_hwpt_alloc hwpt;
>   	struct iommu_hwpt_get_dirty_bitmap get_dirty_bitmap;
>   	struct iommu_hwpt_set_dirty_tracking set_dirty_tracking;
> +	struct iommu_hwpt_invalidate cache;
>   	struct iommu_ioas_alloc alloc;
>   	struct iommu_ioas_allow_iovas allow_iovas;
>   	struct iommu_ioas_copy ioas_copy;
> @@ -348,6 +349,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
>   		 struct iommu_hwpt_get_dirty_bitmap, data),
>   	IOCTL_OP(IOMMU_HWPT_SET_DIRTY_TRACKING, iommufd_hwpt_set_dirty_tracking,
>   		 struct iommu_hwpt_set_dirty_tracking, __reserved),
> +	IOCTL_OP(IOMMU_HWPT_INVALIDATE, iommufd_hwpt_invalidate,
> +		 struct iommu_hwpt_invalidate, out_driver_error_code),
>   	IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
>   		 struct iommu_ioas_alloc, out_ioas_id),
>   	IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 0b2bc6252e2c..7f92cecc87d7 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -49,6 +49,7 @@ enum {
>   	IOMMUFD_CMD_GET_HW_INFO,
>   	IOMMUFD_CMD_HWPT_SET_DIRTY_TRACKING,
>   	IOMMUFD_CMD_HWPT_GET_DIRTY_BITMAP,
> +	IOMMUFD_CMD_HWPT_INVALIDATE,
>   };
>   
>   /**
> @@ -613,4 +614,38 @@ struct iommu_hwpt_get_dirty_bitmap {
>   #define IOMMU_HWPT_GET_DIRTY_BITMAP _IO(IOMMUFD_TYPE, \
>   					IOMMUFD_CMD_HWPT_GET_DIRTY_BITMAP)
>   
> +/**
> + * struct iommu_hwpt_invalidate - ioctl(IOMMU_HWPT_INVALIDATE)
> + * @size: sizeof(struct iommu_hwpt_invalidate)
> + * @hwpt_id: HWPT ID of a nested HWPT for cache invalidation
> + * @reqs_uptr: User pointer to an array having @req_num of cache invalidation
> + *             requests. The request entries in the array are of fixed width
> + *             @req_len, and contain a user data structure for invalidation
> + *             request specific to the given hardware page table.
> + * @req_type: One of enum iommu_hwpt_data_type, defining the data type of all
> + *            the entries in the invalidation request array. It should suit
> + *            with the data_type passed per the allocation of the hwpt pointed
> + *            by @hwpt_id.

@Jason and Kevin,

Here a check with you two. I had a conversation with Nic on the definition
of req_type here. It was added to support potential multiple kinds of cache
invalidation data types for a invalidating cache for a single hwpt type[1].
But we defined it as reusing the hwpt_data_type. In this way, it is not
able to support the potential case in[1]. is it? Shall we define a separate
enum for invalidation data types? And how can we let user know the
available invalidation data types for a hwpt type? Any idea?

[1] https://lore.kernel.org/linux-iommu/20231018163720.GA3952@nvidia.com/


> + * @req_len: Length (in bytes) of a request entry in the request array
> + * @req_num: Input the number of cache invalidation requests in the array.
> + *           Output the number of requests successfully handled by kernel.
> + * @out_driver_error_code: Report a driver speicifc error code upon failure.
> + *                         It's optional, driver has a choice to fill it or
> + *                         not.
> + *
> + * Invalidate the iommu cache for user-managed page table. Modifications on a
> + * user-managed page table should be followed by this operation to sync cache.
> + * Each ioctl can support one or more cache invalidation requests in the array
> + * that has a total size of @req_len * @req_num.
> + */
> +struct iommu_hwpt_invalidate {
> +	__u32 size;
> +	__u32 hwpt_id;
> +	__aligned_u64 reqs_uptr;
> +	__u32 req_type;
> +	__u32 req_len;
> +	__u32 req_num;
> +	__u32 out_driver_error_code;
> +};
> +#define IOMMU_HWPT_INVALIDATE _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_INVALIDATE)
>   #endif

-- 
Regards,
Yi Liu