linux-kernel - Re: [PATCH] riscv: Move user-visible sbi ext ids to uapi

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Message-ID: <20250923-5498566fbd48a3dfd61ecd08@orel>
Date: Tue, 23 Sep 2025 15:14:11 -0500
From: Andrew Jones <ajones@...tanamicro.com>
To: BillXiang <xiangwencheng@...xincomputing.com>
Cc: anup@...infault.org, kvm-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, paul.walmsley@...ive.com, palmer@...belt.com, 
	aou@...s.berkeley.edu, alex@...ti.fr, atishp@...osinc.com
Subject: Re: [PATCH] riscv: Move user-visible sbi ext ids to uapi

On Wed, Sep 17, 2025 at 04:52:46PM +0800, BillXiang wrote:
> Move those sbi ext ids to uapi because they will be forwarded
> to user space by kvm.

We don't need to publish the IDs in UAPI since they are already known to
userspace by reading the SBI spec. Indeed QEMU already defines all of
these except for the experimental range.

What problem are you trying to solve?

Thanks,
drew

> 
> Signed-off-by: BillXiang <xiangwencheng@...xincomputing.com>
> ---
>  arch/riscv/include/asm/sbi.h      | 16 +-----------
>  arch/riscv/include/uapi/asm/sbi.h | 43 +++++++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+), 15 deletions(-)
>  create mode 100644 arch/riscv/include/uapi/asm/sbi.h
> 
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 341e74238aa0..e196feaabb2e 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -10,13 +10,12 @@
>  #include <linux/types.h>
>  #include <linux/cpumask.h>
>  #include <linux/jump_label.h>
> +#include <uapi/asm/sbi.h>
>  
>  #ifdef CONFIG_RISCV_SBI
>  enum sbi_ext_id {
>  #ifdef CONFIG_RISCV_SBI_V01
>  	SBI_EXT_0_1_SET_TIMER = 0x0,
> -	SBI_EXT_0_1_CONSOLE_PUTCHAR = 0x1,
> -	SBI_EXT_0_1_CONSOLE_GETCHAR = 0x2,
>  	SBI_EXT_0_1_CLEAR_IPI = 0x3,
>  	SBI_EXT_0_1_SEND_IPI = 0x4,
>  	SBI_EXT_0_1_REMOTE_FENCE_I = 0x5,
> @@ -37,13 +36,6 @@ enum sbi_ext_id {
>  	SBI_EXT_NACL = 0x4E41434C,
>  	SBI_EXT_FWFT = 0x46574654,
>  
> -	/* Experimentals extensions must lie within this range */
> -	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
> -	SBI_EXT_EXPERIMENTAL_END = 0x08FFFFFF,
> -
> -	/* Vendor extensions must lie within this range */
> -	SBI_EXT_VENDOR_START = 0x09000000,
> -	SBI_EXT_VENDOR_END = 0x09FFFFFF,
>  };
>  
>  enum sbi_ext_base_fid {
> @@ -263,12 +255,6 @@ enum sbi_pmu_ctr_type {
>  #define SBI_PMU_STOP_FLAG_RESET BIT(0)
>  #define SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT BIT(1)
>  
> -enum sbi_ext_dbcn_fid {
> -	SBI_EXT_DBCN_CONSOLE_WRITE = 0,
> -	SBI_EXT_DBCN_CONSOLE_READ = 1,
> -	SBI_EXT_DBCN_CONSOLE_WRITE_BYTE = 2,
> -};
> -
>  /* SBI STA (steal-time accounting) extension */
>  enum sbi_ext_sta_fid {
>  	SBI_EXT_STA_STEAL_TIME_SET_SHMEM = 0,
> diff --git a/arch/riscv/include/uapi/asm/sbi.h b/arch/riscv/include/uapi/asm/sbi.h
> new file mode 100644
> index 000000000000..d29ac0abeefe
> --- /dev/null
> +++ b/arch/riscv/include/uapi/asm/sbi.h
> @@ -0,0 +1,43 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * Copyright (C) 2025 Lanxincomputing Corporation or its affiliates.
> + *
> + * Authors:
> + *     BillXiang <xiangwencheng@...xincomputing.com>
> + */
> +
> +#ifndef _UAPI_ASM_RISCV_SBI_H
> +#define _UAPI_ASM_RISCV_SBI_H
> +
> +
> +enum SBI_EXT_ID {
> +	/*
> +	* The CONSOLE_GETCHAR/CONSOLE_PUTCHAR SBI calls cannot be
> +	* handled in kernel so they will be forwarded to userspace by kvm.
> +	*/
> +	SBI_EXT_0_1_CONSOLE_PUTCHAR = 0x1,
> +	SBI_EXT_0_1_CONSOLE_GETCHAR = 0x2,
> +	/*
> +	* Both SBI experimental and vendor extensions are
> +	* unconditionally forwarded to userspace by kvm.
> +	*/
> +	/* Experimentals extensions must lie within this range */
> +	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
> +	SBI_EXT_EXPERIMENTAL_END = 0x08FFFFFF,
> +
> +	/* Vendor extensions must lie within this range */
> +	SBI_EXT_VENDOR_START = 0x09000000,
> +	SBI_EXT_VENDOR_END = 0x09FFFFFF,
> +};
> +
> +/*
> +* The SBI debug console functions are unconditionally
> +* forwarded to the userspace by kvm.
> +*/
> +enum sbi_ext_dbcn_fid {
> +	SBI_EXT_DBCN_CONSOLE_WRITE = 0,
> +	SBI_EXT_DBCN_CONSOLE_READ = 1,
> +	SBI_EXT_DBCN_CONSOLE_WRITE_BYTE = 2,
> +};
> +
> +#endif /* _UAPI_ASM_RISCV_SBI_H */
> \ No newline at end of file
> -- 
> 2.43.0