linux-kernel - Re: [PATCH 2/3] riscv: Strengthen duplicate and inconsistent definition of RV

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Message-ID: <20250425-93c9f462a1980ebd7bbc515d@orel>
Date: Fri, 25 Apr 2025 09:26:33 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>, 
	Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	kvm-riscv@...ts.infradead.org
Subject: Re: [PATCH 2/3] riscv: Strengthen duplicate and inconsistent
 definition of RV_X()

On Thu, Apr 24, 2025 at 10:45:46AM +0200, Andrew Jones wrote:
> On Tue, Apr 22, 2025 at 10:25:44AM +0200, Alexandre Ghiti wrote:
> > RV_X() macro is defined in two different ways which is error prone.
> > 
> > So harmonize its first definition and add another macro RV_X_mask() for
> > the second one.
> > 
> > Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> > ---
> >  arch/riscv/include/asm/insn.h        | 39 ++++++++++++++--------------
> >  arch/riscv/kernel/elf_kexec.c        |  1 -
> >  arch/riscv/kernel/traps_misaligned.c |  1 -
> >  arch/riscv/kvm/vcpu_insn.c           |  1 -
> >  4 files changed, 20 insertions(+), 22 deletions(-)
> > 
> > diff --git a/arch/riscv/include/asm/insn.h b/arch/riscv/include/asm/insn.h
> > index 2a589a58b291..4063ca35be9b 100644
> > --- a/arch/riscv/include/asm/insn.h
> > +++ b/arch/riscv/include/asm/insn.h
> > @@ -288,43 +288,44 @@ static __always_inline bool riscv_insn_is_c_jalr(u32 code)
> >  
> >  #define RV_IMM_SIGN(x) (-(((x) >> 31) & 1))
> >  #define RVC_IMM_SIGN(x) (-(((x) >> 12) & 1))
> > -#define RV_X(X, s, mask)  (((X) >> (s)) & (mask))
> > -#define RVC_X(X, s, mask) RV_X(X, s, mask)
> > +#define RV_X(X, s, n) (((X) >> (s)) & ((1 << (n)) - 1))
> 
> Assuming n is arbitrary then we should be using BIT_ULL.
>

Eh, scratch this. We know n has to be 31 or less since these macros are
for instruction encodings.

Thanks,
drew