From 99c1e4eb6a3fbbec27c7c70e5fce15cdc1422893 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 20 May 2025 12:54:33 +0800 Subject: ublk: register buffer to local io_uring with provided buf index via UBLK_F_AUTO_BUF_REG Add UBLK_F_AUTO_BUF_REG for supporting to register buffer automatically to local io_uring context with provided buffer index. Add UAPI structure `struct ublk_auto_buf_reg` for holding user parameter to register request buffer automatically, one 'flags' field is defined, and there is still 32bit available for future extension, such as, adding one io_ring FD field for registering buffer to external io_uring. `struct ublk_auto_buf_reg` is populated from ublk uring_cmd's sqe->addr, and all existing ublk commands are data-less, so it is just fine to reuse sqe->addr for this purpose. Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20250520045455.515691-4-ming.lei@redhat.com Signed-off-by: Jens Axboe --- include/uapi/linux/ublk_cmd.h | 64 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) (limited to 'include/uapi') diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index be5c6c6b16e0..f6f516b1223b 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -219,6 +219,29 @@ */ #define UBLK_F_UPDATE_SIZE (1ULL << 10) +/* + * request buffer is registered automatically to uring_cmd's io_uring + * context before delivering this io command to ublk server, meantime + * it is un-registered automatically when completing this io command. + * + * For using this feature: + * + * - ublk server has to create sparse buffer table + * + * - ublk server passes auto buf register data via uring_cmd's sqe->addr, + * `struct ublk_auto_buf_reg` is populated from sqe->addr, please see + * the definition of ublk_sqe_addr_to_auto_buf_reg() + * + * - pass buffer index from `ublk_auto_buf_reg.index` + * + * - all reserved fields in `ublk_auto_buf_reg` need to be zeroed + * + * This way avoids extra cost from two uring_cmd, but also simplifies backend + * implementation, such as, the dependency on IO_REGISTER_IO_BUF and + * IO_UNREGISTER_IO_BUF becomes not necessary. + */ +#define UBLK_F_AUTO_BUF_REG (1ULL << 11) + /* device state */ #define UBLK_S_DEV_DEAD 0 #define UBLK_S_DEV_LIVE 1 @@ -339,6 +362,47 @@ static inline __u32 ublksrv_get_flags(const struct ublksrv_io_desc *iod) return iod->op_flags >> 8; } +struct ublk_auto_buf_reg { + /* index for registering the delivered request buffer */ + __u16 index; + __u16 reserved0; + + /* + * io_ring FD can be passed via the reserve field in future for + * supporting to register io buffer to external io_uring + */ + __u32 reserved1; +}; + +/* + * For UBLK_F_AUTO_BUF_REG, auto buffer register data is carried via + * uring_cmd's sqe->addr: + * + * - bit0 ~ bit15: buffer index + * - bit24 ~ bit31: reserved0 + * - bit32 ~ bit63: reserved1 + */ +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, + .reserved0 = (sqe_addr >> 16) & 0xffff, + .reserved1 = sqe_addr >> 32, + }; + + return reg; +} + +static inline __u64 +ublk_auto_buf_reg_to_sqe_addr(const struct ublk_auto_buf_reg *buf) +{ + __u64 addr = buf->index | (__u64)buf->reserved0 << 16 | + (__u64)buf->reserved1 << 32; + + return addr; +} + /* issued to ublk driver via /dev/ublkcN */ struct ublksrv_io_cmd { __u16 q_id; -- cgit v1.2.3