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 compatiable 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 mapped by the @out_data_type field.
As only physical devices have IOMMU hardware, so this will return error if the given device is not a physical device.
Co-developed-by: Nicolin Chen nicolinc@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com Signed-off-by: Yi Liu yi.l.liu@intel.com --- drivers/iommu/iommufd/main.c | 79 ++++++++++++++++++++++++++++++++++++ include/uapi/linux/iommufd.h | 36 ++++++++++++++++ 2 files changed, 115 insertions(+)
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c index 94c498b8fdf6..a0302bcaa97c 100644 --- a/drivers/iommu/iommufd/main.c +++ b/drivers/iommu/iommufd/main.c @@ -17,6 +17,7 @@ #include <linux/bug.h> #include <uapi/linux/iommufd.h> #include <linux/iommufd.h> +#include "../iommu-priv.h"
#include "io_pagetable.h" #include "iommufd_private.h" @@ -177,6 +178,81 @@ static int iommufd_destroy(struct iommufd_ucmd *ucmd) return 0; }
+static int iommufd_zero_fill_user(void __user *ptr, size_t bytes) +{ + int index = 0; + + for (; index < bytes; index++) { + if (put_user(0, (uint8_t __user *)(ptr + index))) + return -EFAULT; + } + return 0; +} + +static int iommufd_get_hw_info(struct iommufd_ucmd *ucmd) +{ + u32 hw_info_type = IOMMU_HW_INFO_TYPE_NONE; + struct iommu_hw_info *cmd = ucmd->cmd; + unsigned int length = 0, data_len; + struct iommufd_device *idev; + const struct iommu_ops *ops; + void __user *user_ptr; + void *data = NULL; + int rc = 0; + + if (cmd->flags || cmd->__reserved || !cmd->data_len) + return -EOPNOTSUPP; + + idev = iommufd_get_device(ucmd, cmd->dev_id); + if (IS_ERR(idev)) + return PTR_ERR(idev); + + user_ptr = u64_to_user_ptr(cmd->data_ptr); + + ops = dev_iommu_ops(idev->dev); + if (!ops->hw_info) + goto done; + + data = ops->hw_info(idev->dev, &data_len, &hw_info_type); + if (IS_ERR(data)) { + rc = PTR_ERR(data); + goto out_err; + } + + /* driver has hw_info callback should have a unique hw_info_type */ + if (WARN_ON_ONCE(hw_info_type == IOMMU_HW_INFO_TYPE_NONE)) { + rc = -ENODEV; + goto out_err; + } + + length = min(cmd->data_len, data_len); + if (copy_to_user(user_ptr, data, length)) { + rc = -EFAULT; + goto out_err; + } + +done: + /* + * Zero the trailing bytes if the user buffer is bigger than the + * data size kernel actually has. + */ + if (length < cmd->data_len) { + rc = iommufd_zero_fill_user(user_ptr + length, + cmd->data_len - length); + if (rc) + goto out_err; + } + + cmd->data_len = length; + cmd->out_data_type = hw_info_type; + rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd)); + +out_err: + kfree(data); + iommufd_put_object(&idev->obj); + return rc; +} + static int iommufd_fops_open(struct inode *inode, struct file *filp) { struct iommufd_ctx *ictx; @@ -265,6 +341,7 @@ static int iommufd_option(struct iommufd_ucmd *ucmd)
union ucmd_buffer { struct iommu_destroy destroy; + struct iommu_hw_info info; struct iommu_hwpt_alloc hwpt; struct iommu_ioas_alloc alloc; struct iommu_ioas_allow_iovas allow_iovas; @@ -297,6 +374,8 @@ struct iommufd_ioctl_op { } static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = { IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id), + 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), IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl, diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h index 1f616b0f8ae0..4295362e7b44 100644 --- a/include/uapi/linux/iommufd.h +++ b/include/uapi/linux/iommufd.h @@ -46,6 +46,7 @@ enum { IOMMUFD_CMD_OPTION, IOMMUFD_CMD_VFIO_IOAS, IOMMUFD_CMD_HWPT_ALLOC, + IOMMUFD_CMD_GET_HW_INFO, };
/** @@ -378,4 +379,39 @@ struct iommu_hwpt_alloc { enum iommu_hw_info_type { IOMMU_HW_INFO_TYPE_NONE, }; + +/** + * struct iommu_hw_info - ioctl(IOMMU_GET_HW_INFO) + * @size: sizeof(struct iommu_hw_info) + * @flags: Must be 0 + * @dev_id: The device bound to the iommufd + * @data_len: Input the length of the user buffer in bytes. Output the length + * of data filled in the user buffer. + * @data_ptr: Pointer to the user buffer + * @out_data_type: Output the iommu hardware info type as defined in the enum + * iommu_hw_info_type. + * @__reserved: Must be 0 + * + * Query the hardware information from an iommu behind a given device that has + * been bound to iommufd. @data_len is the size of the buffer, which captures an + * iommu type specific input data and a filled output data. Trailing bytes will + * be zeroed if the user buffer is larger than the data kernel has. + * + * The type specific data would be used to sync capabilities between the virtual + * IOMMU and the hardware IOMMU, e.g. a nested translation setup needs to check + * the hardware information, so the guest stage-1 page table will be compatible. + * + * The @out_data_type will be filled if the ioctl succeeds. It would be used to + * decode the data filled in the buffer pointed by @data_ptr. + */ +struct iommu_hw_info { + __u32 size; + __u32 flags; + __u32 dev_id; + __u32 data_len; + __aligned_u64 data_ptr; + __u32 out_data_type; + __u32 __reserved; +}; +#define IOMMU_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_GET_HW_INFO) #endif