Re: [PATCH v6 07/24] RISC-V: Use the minor version mask while computing sbi version

From: Andrew Jones <ajones@ventanamicro.com>
To: Atish Patra <atishp@rivosinc.com>
Cc: linux-kernel@vger.kernel.org,
	Ajay Kaher <ajay.kaher@broadcom.com>,
	 Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alexghiti@rivosinc.com>,
	 Alexey Makhalov <alexey.amakhalov@broadcom.com>,
	Anup Patel <anup@brainfault.org>,
	 Atish Patra <atishp@atishpatra.org>,
	 Broadcom internal kernel review list
	<bcm-kernel-feedback-list@broadcom.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	 Juergen Gross <jgross@suse.com>,
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
	 linux-kselftest@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	 Mark Rutland <mark.rutland@arm.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Paolo Bonzini <pbonzini@redhat.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	 Shuah Khan <shuah@kernel.org>,
	virtualization@lists.linux.dev, Will Deacon <will@kernel.org>,
	 x86@kernel.org
Subject: Re: [PATCH v6 07/24] RISC-V: Use the minor version mask while computing sbi version
Date: Tue, 16 Apr 2024 10:49:20 +0200	[thread overview]
Message-ID: <20240416-1a9f7ea9700c4c6c3e52a1b1@orel> (raw)
In-Reply-To: <2a63d7da-91b6-496d-9966-e6c0a0aa6c6c@rivosinc.com>

On Tue, Apr 16, 2024 at 01:31:27AM -0700, Atish Patra wrote:
> On 4/15/24 06:06, Andrew Jones wrote:
> > On Wed, Apr 10, 2024 at 05:07:35PM -0700, Atish Patra wrote:
> > > As per the SBI specification, minor version is encoded in the
> > > lower 24 bits only. Make sure that the SBI version is computed
> > > with the appropriate mask.
> > > 
> > > Currently, there is no minor version in use. Thus, it doesn't
> > > change anything functionality but it is good to be compliant with
> > > the specification.
> > > 
> > > Signed-off-by: Atish Patra <atishp@rivosinc.com>
> > > ---
> > >   arch/riscv/include/asm/sbi.h | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> > > index f31650b10899..935b082d6a6c 100644
> > > --- a/arch/riscv/include/asm/sbi.h
> > > +++ b/arch/riscv/include/asm/sbi.h
> > > @@ -367,8 +367,8 @@ static inline unsigned long sbi_minor_version(void)
> > >   static inline unsigned long sbi_mk_version(unsigned long major,
> > >   					    unsigned long minor)
> > >   {
> > > -	return ((major & SBI_SPEC_VERSION_MAJOR_MASK) <<
> > > -		SBI_SPEC_VERSION_MAJOR_SHIFT) | minor;
> > > +	return ((major & SBI_SPEC_VERSION_MAJOR_MASK) << SBI_SPEC_VERSION_MAJOR_SHIFT
> > > +		| (minor & SBI_SPEC_VERSION_MINOR_MASK));
> > 
> > The previous version had ((major & major_mask) << major_shift) | minor
> > (parentheses around all the major bits before the OR). Now we have
> > parentheses around everything, which aren't necessary, and no longer
> 
> We have to use parentheses around | to avoid compiler warnings
> (-Wparentheses)
> 
> Are you only concerned about the outer parentheses ? I have removed it.
> 
> > have them around all the major bits before the OR. We don't need the
> > parentheses around the major bits, since shift has higher precedence
> > than OR, but I'd probably keep them.
> > 
> 
> Is this what you prefer?
> 
> return ((major & SBI_SPEC_VERSION_MAJOR_MASK) <<
> SBI_SPEC_VERSION_MAJOR_SHIFT) | (minor & SBI_SPEC_VERSION_MINOR_MASK);

Yup

Thanks,
drew

> 
> 
> 
> 
> > Otherwise,
> > 
> > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> > 
> > >   }
> > >   int sbi_err_map_linux_errno(int err);
> > > -- 
> > > 2.34.1
> > > 
> > 
> > _______________________________________________
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>