Re: [PATCH v4 2/4] xen/riscv: introduce sbi call to putchar to console

[Bobby Eshleman <bobbyeshleman@xxxxxxxxx>]

On Mon, Jan 16, 2023 at 04:39:30PM +0200, Oleksii Kurochko wrote:
> From: Bobby Eshleman <bobby.eshleman@xxxxxxxxx>
> 
> Originally SBI implementation for Xen was introduced by
> Bobby Eshleman <bobby.eshleman@xxxxxxxxx> but it was removed
> all the stuff for simplicity  except SBI call for putting
> character to console.
> 
> The patch introduces sbi_putchar() SBI call which is necessary
> to implement initial early_printk.
> 
> Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxx>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> ---
> Changes in V4:
>     - Nothing changed
> ---
> Changes in V3:
>     - update copyright's year
>     - rename definition of __CPU_SBI_H__ to __ASM_RISCV_SBI_H__
>     - fix identations
>     - change an author of the commit
> ---
> Changes in V2:
>     - add an explanatory comment about sbi_console_putchar() function.
>     - order the files alphabetically in Makefile
> ---
>  xen/arch/riscv/Makefile          |  1 +
>  xen/arch/riscv/include/asm/sbi.h | 34 ++++++++++++++++++++++++
>  xen/arch/riscv/sbi.c             | 45 ++++++++++++++++++++++++++++++++
>  3 files changed, 80 insertions(+)
>  create mode 100644 xen/arch/riscv/include/asm/sbi.h
>  create mode 100644 xen/arch/riscv/sbi.c
> 
> diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
> index 5a67a3f493..fd916e1004 100644
> --- a/xen/arch/riscv/Makefile
> +++ b/xen/arch/riscv/Makefile
> @@ -1,4 +1,5 @@
>  obj-$(CONFIG_RISCV_64) += riscv64/
> +obj-y += sbi.o
>  obj-y += setup.o
>  
>  $(TARGET): $(TARGET)-syms
> diff --git a/xen/arch/riscv/include/asm/sbi.h 
> b/xen/arch/riscv/include/asm/sbi.h
> new file mode 100644
> index 0000000000..0e6820a4ed
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/sbi.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: (GPL-2.0-or-later) */
> +/*
> + * Copyright (c) 2021-2023 Vates SAS.
> + *
> + * Taken from xvisor, modified by Bobby Eshleman (bobby.eshleman@xxxxxxxxx).
> + *
> + * Taken/modified from Xvisor project with the following copyright:
> + *
> + * Copyright (c) 2019 Western Digital Corporation or its affiliates.
> + */
> +
> +#ifndef __ASM_RISCV_SBI_H__
> +#define __ASM_RISCV_SBI_H__
> +
> +#define SBI_EXT_0_1_CONSOLE_PUTCHAR          0x1
> +
> +struct sbiret {
> +    long error;
> +    long value;
> +};
> +
> +struct sbiret sbi_ecall(unsigned long ext, unsigned long fid,
> +                        unsigned long arg0, unsigned long arg1,
> +                        unsigned long arg2, unsigned long arg3,
> +                        unsigned long arg4, unsigned long arg5);
> +
> +/**
> + * Writes given character to the console device.
> + *
> + * @param ch The data to be written to the console.
> + */
> +void sbi_console_putchar(int ch);
> +
> +#endif /* __ASM_RISCV_SBI_H__ */
> diff --git a/xen/arch/riscv/sbi.c b/xen/arch/riscv/sbi.c
> new file mode 100644
> index 0000000000..dc0eb44bc6
> --- /dev/null
> +++ b/xen/arch/riscv/sbi.c
> @@ -0,0 +1,45 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Taken and modified from the xvisor project with the copyright Copyright 
> (c)
> + * 2019 Western Digital Corporation or its affiliates and author Anup Patel
> + * (anup.patel@xxxxxxx).
> + *
> + * Modified by Bobby Eshleman (bobby.eshleman@xxxxxxxxx).
> + *
> + * Copyright (c) 2019 Western Digital Corporation or its affiliates.
> + * Copyright (c) 2021-2023 Vates SAS.
> + */
> +
> +#include <xen/errno.h>
> +#include <asm/sbi.h>
> +
> +struct sbiret sbi_ecall(unsigned long ext, unsigned long fid,
> +                        unsigned long arg0, unsigned long arg1,
> +                        unsigned long arg2, unsigned long arg3,
> +                        unsigned long arg4, unsigned long arg5)
> +{
> +    struct sbiret ret;
> +
> +    register unsigned long a0 asm ("a0") = arg0;
> +    register unsigned long a1 asm ("a1") = arg1;
> +    register unsigned long a2 asm ("a2") = arg2;
> +    register unsigned long a3 asm ("a3") = arg3;
> +    register unsigned long a4 asm ("a4") = arg4;
> +    register unsigned long a5 asm ("a5") = arg5;
> +    register unsigned long a6 asm ("a6") = fid;
> +    register unsigned long a7 asm ("a7") = ext;
> +
> +    asm volatile ("ecall"
> +              : "+r" (a0), "+r" (a1)
> +              : "r" (a2), "r" (a3), "r" (a4), "r" (a5), "r" (a6), "r" (a7)
> +              : "memory");
> +    ret.error = a0;
> +    ret.value = a1;
> +
> +    return ret;
> +}
> +
> +void sbi_console_putchar(int ch)
> +{
> +    sbi_ecall(SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, ch, 0, 0, 0, 0, 0);
> +}
> -- 
> 2.39.0
> 
> 

Reviewed-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxx>