Re: [PATCH v6 05/10] iommufd: Add fault and response message definitions

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

On 6/12/24 9:52 PM, Jason Gunthorpe wrote:
> On Mon, May 27, 2024 at 12:05:12PM +0800, Lu Baolu wrote:
>> +/**
>> + * 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: Fault address
>> + * @length: a hint of how much data the requestor is expecting to fetch. For
>> + *          example, if the PRI initiator knows it is going to do a 10MB
>> + *          transfer, it could fill in 10MB and the OS could pre-fault in
>> + *          10MB of IOVA. It's default to 0 if there's no such hint.
>> + * @cookie: kernel-managed cookie identifying a group of fault messages. The
>> + *          cookie number encoded in the last page fault of the group should
>> + *          be echoed back in the response message.
>> + */
>> +struct iommu_hwpt_pgfault {
>> +	__u32 size;
> Given we fail the system call if size is not exactly the right value
> we should probably drop it here.
> 
> The ioctl to get the FD can someday specify the format of the fault
> messages if we need to upgrade. If we want to change it down the road
> then the old FD will be exactly as it is now, and the user will
> request a new format FD that only works in whatever the new way is.

Okay, sure!

Best regards,
baolu