From: Nicolin Chen nicolinc@nvidia.com Sent: Friday, August 18, 2023 5:08 AM
Looks like Yi's latest code has not addressed these comments.
Yeah. Not yet. In progress to incorporate them. 😊
On Thu, Aug 17, 2023 at 07:31:42AM +0000, Tian, Kevin wrote:
From: Liu, Yi L yi.l.liu@intel.com Sent: Wednesday, August 16, 2023 8:14 PM
Under nested IOMMU translation, userspace owns the stage-1 translation table (e.g. the stage-1 page table of Intel VT-d or the context table of ARM SMMUv3, and etc.). Stage-1 translation tables are vendor specific, and need to be compatible with the underlying IOMMU hardware. Hence, userspace should know the IOMMU hardware capability before creating and configuring the stage-1 translation table to kernel.
This adds IOMMU_GET_HW_INFO ioctl to query the IOMMU hardware information (a.k.a capability) for a given device. The returned data is vendor specific, userspace needs to decode it with the structure by the output @out_data_type field.
"The format of the returned data is vendor specific and must be decoded according to @out_data_type field".
Ack.
+int iommufd_get_hw_info(struct iommufd_ucmd *ucmd) +{
struct iommu_hw_info *cmd = ucmd->cmd;void __user *user_ptr = u64_to_user_ptr(cmd->data_uptr);const struct iommu_ops *ops;struct iommufd_device *idev;unsigned int data_len;unsigned int copy_len;void *data = NULL;[..]
} else {cmd->out_data_type = IOMMU_HW_INFO_TYPE_NONE;data_len = 0;data = NULL;data is already initialized as NULL.
Probably we can set data_len = 0 and the out_data_type to _NONE is the top as well. Any preference?
Will drop.
/** We return the length the kernel supports so userspace may knowwhat
* the kernel capability is. It could be larger than the input buffer.*/cmd->data_len = data_len;rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));+out:
out_free:
kfree(data);+err_put:
out_put: (since this is also used in the success path)
Ack for both.
- To capture an iommu type specific hardware information data,
@data_uptr and
- its length @data_len must be provided. Trailing bytes will be zeroed if the
- user buffer is larger than the data that kernel has. Otherwise, kernel only
- fills the buffer using the given length in @data_len. If the ioctl succeeds,
- @data_len will be updated to the length that kernel actually supports,
- @out_data_type will be filled to decode the data filled in the buffer
- pointed by @data_uptr. Input @data_len == zero is allowed, no
information
- data will be filled to user, but user space could get the
iommu_hw_info_type
- filled in @out_data_type and the iommu hardware information data
length
- supported by kernel filled in @data_len.
I'd just keep "Input @data_len == zero is allowed" and remove all the trailing words which just duplicate with the former context.
Will do.
Reviewed-by: Kevin Tian kevin.tian@intel.com
Adding this.
Thanks Nic