linux-kernel - Re: [RFC PATCH 1/2] RISC-V: Mark existing SBI as legacy SBI.

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Date:   Tue, 27 Aug 2019 07:03:04 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Atish Patra <atish.patra@....com>
Cc:     linux-kernel@...r.kernel.org, Albert Ou <aou@...s.berkeley.edu>,
        Alan Kao <alankao@...estech.com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Anup Patel <anup@...infault.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Gary Guo <gary@...yguo.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-riscv@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 1/2] RISC-V: Mark existing SBI as legacy SBI.

> +#define SBI_EXT_LEGACY_SET_TIMER 0x0
> +#define SBI_EXT_LEGACY_CONSOLE_PUTCHAR 0x1
> +#define SBI_EXT_LEGACY_CONSOLE_GETCHAR 0x2
> +#define SBI_EXT_LEGACY_CLEAR_IPI 0x3
> +#define SBI_EXT_LEGACY_SEND_IPI 0x4
> +#define SBI_EXT_LEGACY_REMOTE_FENCE_I 0x5
> +#define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA 0x6
> +#define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA_ASID 0x7
> +#define SBI_EXT_LEGACY_SHUTDOWN 0x8

As Mike said legacy is a bit of a weird name.  I think this should
be SBI01_* or so.  And pleae align the numeric values and maybe use
an enum.

> +
> +#define SBI_CALL_LEGACY(which, arg0, arg1, arg2, arg3) ({             \
>  	register uintptr_t a0 asm ("a0") = (uintptr_t)(arg0);	\
>  	register uintptr_t a1 asm ("a1") = (uintptr_t)(arg1);	\
>  	register uintptr_t a2 asm ("a2") = (uintptr_t)(arg2);	\

Instead of the weird inline assembly with forced register allocation,
why not move this to pure assembly?  AFAICs this is the whole assembly
code we'd need:

ENTRY(sbi01_call)
        ecall
END(sbi01_call)

>  /* Lazy implementations until SBI is finalized */
> -#define SBI_CALL_0(which) SBI_CALL(which, 0, 0, 0, 0)
> -#define SBI_CALL_1(which, arg0) SBI_CALL(which, arg0, 0, 0, 0)
> -#define SBI_CALL_2(which, arg0, arg1) SBI_CALL(which, arg0, arg1, 0, 0)
> -#define SBI_CALL_3(which, arg0, arg1, arg2) \
> -		SBI_CALL(which, arg0, arg1, arg2, 0)
> -#define SBI_CALL_4(which, arg0, arg1, arg2, arg3) \
> -		SBI_CALL(which, arg0, arg1, arg2, arg3)
> +#define SBI_CALL_LEGACY_0(which) SBI_CALL_LEGACY(which, 0, 0, 0, 0)
> +#define SBI_CALL_LEGACY_1(which, arg0) SBI_CALL_LEGACY(which, arg0, 0, 0, 0)
> +#define SBI_CALL_LEGACY_2(which, arg0, arg1) \
> +		SBI_CALL_LEGACY(which, arg0, arg1, 0, 0)
> +#define SBI_CALL_LEGACY_3(which, arg0, arg1, arg2) \
> +		SBI_CALL_LEGACY(which, arg0, arg1, arg2, 0)
> +#define SBI_CALL_LEGACY_4(which, arg0, arg1, arg2, arg3) \
> +		SBI_CALL_LEGACY(which, arg0, arg1, arg2, arg3)

When you touch this anyway I'd suggest you kill these rather
pointless wrappers as well as the comment above them.