linux-kernel - Re: [PATCH v2 2/6] iommufd: Add iommu page fault uapi data

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Message-ID: <20231201151405.GA1489931@ziepe.ca>
Date:   Fri, 1 Dec 2023 11:14:05 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux.dev, linux-kselftest@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/6] iommufd: Add iommu page fault uapi data

On Thu, Oct 26, 2023 at 10:49:26AM +0800, Lu Baolu wrote:

> + * @IOMMU_HWPT_ALLOC_IOPF_CAPABLE: User is capable of handling IO page faults.

This does not seem like the best name?

Probably like this given my remark in the cover letter:

--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -359,6 +359,7 @@ struct iommu_vfio_ioas {
 enum iommufd_hwpt_alloc_flags {
        IOMMU_HWPT_ALLOC_NEST_PARENT = 1 << 0,
        IOMMU_HWPT_ALLOC_DIRTY_TRACKING = 1 << 1,
+       IOMMU_HWPT_IOPFD_FD_VALID = 1 << 2,
 };
 
 /**
@@ -440,6 +441,7 @@ struct iommu_hwpt_alloc {
        __u32 data_type;
        __u32 data_len;
        __aligned_u64 data_uptr;
+       __s32 iopf_fd;
 };
 #define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_ALLOC)



> @@ -679,6 +688,62 @@ struct iommu_dev_data_arm_smmuv3 {
>  	__u32 sid;
>  };
>  
> +/**
> + * struct iommu_hwpt_pgfault - iommu page fault data
> + * @size: sizeof(struct iommu_hwpt_pgfault)
> + * @flags: Combination of IOMMU_PGFAULT_FLAGS_ flags.
> + *  - PASID_VALID: @pasid field is valid
> + *  - LAST_PAGE: the last page fault in a group
> + *  - PRIV_DATA: @private_data field is valid
> + *  - RESP_NEEDS_PASID: the page response must have the same
> + *                      PASID value as the page request.
> + * @dev_id: id of the originated device
> + * @pasid: Process Address Space ID
> + * @grpid: Page Request Group Index
> + * @perm: requested page permissions (IOMMU_PGFAULT_PERM_* values)
> + * @addr: page address
> + * @private_data: device-specific private information
> + */
> +struct iommu_hwpt_pgfault {
> +	__u32 size;
> +	__u32 flags;
> +#define IOMMU_PGFAULT_FLAGS_PASID_VALID		(1 << 0)
> +#define IOMMU_PGFAULT_FLAGS_LAST_PAGE		(1 << 1)
> +#define IOMMU_PGFAULT_FLAGS_PRIV_DATA		(1 << 2)
> +#define IOMMU_PGFAULT_FLAGS_RESP_NEEDS_PASID	(1 << 3)
> +	__u32 dev_id;
> +	__u32 pasid;
> +	__u32 grpid;
> +	__u32 perm;
> +#define IOMMU_PGFAULT_PERM_READ			(1 << 0)
> +#define IOMMU_PGFAULT_PERM_WRITE		(1 << 1)
> +#define IOMMU_PGFAULT_PERM_EXEC			(1 << 2)
> +#define IOMMU_PGFAULT_PERM_PRIV			(1 << 3)
> +	__u64 addr;
> +	__u64 private_data[2];
> +};

This mixed #define is not the style, these should be in enums,
possibly with kdocs

Use __aligned_u64 also

> +
> +/**
> + * struct iommu_hwpt_response - IOMMU page fault response
> + * @size: sizeof(struct iommu_hwpt_response)
> + * @flags: Must be set to 0
> + * @hwpt_id: hwpt ID of target hardware page table for the response
> + * @dev_id: device ID of target device for the response
> + * @pasid: Process Address Space ID
> + * @grpid: Page Request Group Index
> + * @code: response code. The supported codes include:
> + *        0: Successful; 1: Response Failure; 2: Invalid Request.
> + */
> +struct iommu_hwpt_page_response {
> +	__u32 size;
> +	__u32 flags;
> +	__u32 hwpt_id;
> +	__u32 dev_id;
> +	__u32 pasid;
> +	__u32 grpid;
> +	__u32 code;
> +};

Is it OK to have the user pass in all this detailed information? Is it
a security problem if the user lies? Ie shouldn't we only ack page
faults we actually have outstanding?

IOW should iommu_hwpt_pgfault just have a 'response_cookie' generated
by the kernel that should be placed here? The kernel would keep track
of all this internal stuff?

Jason