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

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Message-ID: <20190827140442.GB21855@infradead.org>
Date:   Tue, 27 Aug 2019 07:04:42 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Atish Patra <atish.patra@....com>
Cc:     Albert Ou <aou@...s.berkeley.edu>,
        Alan Kao <alankao@...estech.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Anup Patel <anup@...infault.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Gary Guo <gary@...yguo.net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 1/2] RISC-V: Mark existing SBI as legacy SBI.

On Tue, Aug 27, 2019 at 07:03:04AM -0700, Christoph Hellwig wrote:
> > +#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)

Actually we'll need a mv to a7 for the function id, but the point
still stands.