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

From: Atish Patra <atishp@rivosinc.com>
To: Andrew Jones <ajones@ventanamicro.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 01:31:27 -0700	[thread overview]
Message-ID: <2a63d7da-91b6-496d-9966-e6c0a0aa6c6c@rivosinc.com> (raw)
In-Reply-To: <20240415-e229bb33ad53ce43e3534f5a@orel>

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); 

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