Re: [PATCH v3 3/8] iommufd: Add fault and response message definitions

[Jason Gunthorpe <jgg@ziepe.ca>]

On Mon, Jan 22, 2024 at 03:38:58PM +0800, Lu Baolu wrote:

> +/**
> + * enum iommu_hwpt_pgfault_flags - flags for struct iommu_hwpt_pgfault
> + * @IOMMU_PGFAULT_FLAGS_PASID_VALID: The pasid field of the fault data is
> + *                                   valid.
> + * @IOMMU_PGFAULT_FLAGS_LAST_PAGE: It's the last fault of a fault group.
> + */
> +enum iommu_hwpt_pgfault_flags {
> +	IOMMU_PGFAULT_FLAGS_PASID_VALID		= (1 << 0),
> +	IOMMU_PGFAULT_FLAGS_LAST_PAGE		= (1 << 1),
> +};
> +
> +/**
> + * enum iommu_hwpt_pgfault_perm - perm bits for struct iommu_hwpt_pgfault
> + * @IOMMU_PGFAULT_PERM_READ: request for read permission
> + * @IOMMU_PGFAULT_PERM_WRITE: request for write permission
> + * @IOMMU_PGFAULT_PERM_EXEC: request for execute permission
> + * @IOMMU_PGFAULT_PERM_PRIV: request for privileged permission

You are going to have to elaborate what PRIV is for.. We don't have
any concept of this in the UAPI for iommufd so what is a userspace
supposed to do if it hits this? EXEC is similar, we can't actually
enable exec permissions from userspace IIRC..

> +enum iommu_hwpt_pgfault_perm {
> +	IOMMU_PGFAULT_PERM_READ			= (1 << 0),
> +	IOMMU_PGFAULT_PERM_WRITE		= (1 << 1),
> +	IOMMU_PGFAULT_PERM_EXEC			= (1 << 2),
> +	IOMMU_PGFAULT_PERM_PRIV			= (1 << 3),
> +};
> +
> +/**
> + * struct iommu_hwpt_pgfault - iommu page fault data
> + * @size: sizeof(struct iommu_hwpt_pgfault)
> + * @flags: Combination of enum iommu_hwpt_pgfault_flags
> + * @dev_id: id of the originated device
> + * @pasid: Process Address Space ID
> + * @grpid: Page Request Group Index
> + * @perm: Combination of enum iommu_hwpt_pgfault_perm
> + * @addr: page address
> + */
> +struct iommu_hwpt_pgfault {
> +	__u32 size;
> +	__u32 flags;
> +	__u32 dev_id;
> +	__u32 pasid;
> +	__u32 grpid;
> +	__u32 perm;
> +	__u64 addr;
> +};

Do we need an addr + size here? I've seen a few things where I wonder
if that might become an enhancment someday.

> +/**
> + * struct iommu_hwpt_page_response - IOMMU page fault response
> + * @size: sizeof(struct iommu_hwpt_page_response)
> + * @flags: Must be set to 0
> + * @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.

This should be an enum

> + * @addr: The fault address. Must match the addr field of the
> + *        last iommu_hwpt_pgfault of a reported iopf group.
> + */
> +struct iommu_hwpt_page_response {
> +	__u32 size;
> +	__u32 flags;
> +	__u32 dev_id;
> +	__u32 pasid;
> +	__u32 grpid;
> +	__u32 code;
> +	__u64 addr;
> +};

Do we want some kind of opaque ID value from the kernel here to match
request with response exactly? Or is the plan to search on the addr?

Jason