diff options
Diffstat (limited to 'include/uapi/linux/ublk_cmd.h')
| -rw-r--r-- | include/uapi/linux/ublk_cmd.h | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index 77d9d6af46da..c9751bdfd937 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -135,8 +135,28 @@ #define UBLKSRV_IO_BUF_TOTAL_SIZE (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS) /* - * zero copy requires 4k block size, and can remap ublk driver's io - * request into ublksrv's vm space + * ublk server can register data buffers for incoming I/O requests with a sparse + * io_uring buffer table. The request buffer can then be used as the data buffer + * for io_uring operations via the fixed buffer index. + * Note that the ublk server can never directly access the request data memory. + * + * To use this feature, the ublk server must first register a sparse buffer + * table on an io_uring instance. + * When an incoming ublk request is received, the ublk server submits a + * UBLK_U_IO_REGISTER_IO_BUF command to that io_uring instance. The + * ublksrv_io_cmd's q_id and tag specify the request whose buffer to register + * and addr is the index in the io_uring's buffer table to install the buffer. + * SQEs can now be submitted to the io_uring to read/write the request's buffer + * by enabling fixed buffers (e.g. using IORING_OP_{READ,WRITE}_FIXED or + * IORING_URING_CMD_FIXED) and passing the registered buffer index in buf_index. + * Once the last io_uring operation using the request's buffer has completed, + * the ublk server submits a UBLK_U_IO_UNREGISTER_IO_BUF command with q_id, tag, + * and addr again specifying the request buffer to unregister. + * The ublk request is completed when its buffer is unregistered from all + * io_uring instances and the ublk server issues UBLK_U_IO_COMMIT_AND_FETCH_REQ. + * + * Not available for UBLK_F_UNPRIVILEGED_DEV, as a ublk server can leak + * uninitialized kernel memory by not reading into the full request buffer. */ #define UBLK_F_SUPPORT_ZERO_COPY (1ULL << 0) @@ -450,10 +470,10 @@ static inline struct ublk_auto_buf_reg ublk_sqe_addr_to_auto_buf_reg( __u64 sqe_addr) { struct ublk_auto_buf_reg reg = { - .index = sqe_addr & 0xffff, - .flags = (sqe_addr >> 16) & 0xff, - .reserved0 = (sqe_addr >> 24) & 0xff, - .reserved1 = sqe_addr >> 32, + .index = (__u16)sqe_addr, + .flags = (__u8)(sqe_addr >> 16), + .reserved0 = (__u8)(sqe_addr >> 24), + .reserved1 = (__u32)(sqe_addr >> 32), }; return reg; |