Re: [PATCH v5 7/9] iommufd: Associate fault object with iommufd_hw_pgtable

Baolu Lu
2024-05-10T03:25:33Z

On 5/8/24 8:25 AM, Jason Gunthorpe wrote:
> On Tue, Apr 30, 2024 at 10:57:08PM +0800, Lu Baolu wrote:
>> /**
>> @@ -412,6 +415,9 @@ enum iommu_hwpt_data_type {
>> * @data_type: One of enum iommu_hwpt_data_type
>> * @data_len: Length of the type specific data
>> * @data_uptr: User pointer to the type specific data
>> + * @fault_id: The ID of IOMMUFD_FAULT object. Valid only if flags field of
>> + * IOMMU_HWPT_FAULT_ID_VALID is set.
>> + * @__reserved2: Padding to 64-bit alignment. Must be 0.
>> *
>> * Explicitly allocate a hardware page table object. This is the same object
>> * type that is returned by iommufd_device_attach() and represents the
>> @@ -442,6 +448,8 @@ struct iommu_hwpt_alloc {
>> __u32 data_type;
>> __u32 data_len;
>> __aligned_u64 data_uptr;
>> + __u32 fault_id;
>> + __u32 __reserved2;
>> };
>> #define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_ALLOC)
> [..]
>
>> @@ -359,7 +359,7 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
>> IOCTL_OP(IOMMU_GET_HW_INFO, iommufd_get_hw_info, struct iommu_hw_info,
>> __reserved),
>> IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc,
>> - __reserved),
>> + __reserved2),
> This is now how the back compat mechanism works. The value here is the
> absolute minimum size, it should never increase. The first __reserved
> is always the right value.
>
> If you change it then old userspace that doesn't include the fault_id
> will stop working.

Yeah! I will remove this change.

Best regards,
baolu