linux-kernel - Re: [PATCH v3 02/22] arm64: Generate sign macro for sysreg Enums

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Message-ID: <gsntecv49aml.fsf@coltonlewis-kvm.c.googlers.com>
Date: Fri, 27 Jun 2025 20:45:38 +0000
From: Colton Lewis <coltonlewis@...gle.com>
To: Ben Horgan <ben.horgan@....com>
Cc: kvm@...r.kernel.org, pbonzini@...hat.com, corbet@....net, 
	linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org, 
	maz@...nel.org, oliver.upton@...ux.dev, mizhang@...gle.com, 
	joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com, 
	mark.rutland@....com, shuah@...nel.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, linux-perf-users@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 02/22] arm64: Generate sign macro for sysreg Enums

Hi Ben. Thanks for the review.

Ben Horgan <ben.horgan@....com> writes:

> Hi Colton,

> On 6/26/25 21:04, Colton Lewis wrote:
>> There's no reason Enums shouldn't be equivalent to UnsignedEnums and
>> explicitly specify they are unsigned. This will avoid the annoyance I
>> had with HPMN0.
> An Enum can be annotated with the field's sign by updating it to
> UnsignedEnum or SignedEnum. This is explained in [1].

> With this change ID_AA64PFR1_EL1.MTE_frac would be marked as unsigned
> when it should really be considered signed.

> Enum	43:40	MTE_frac
> 	0b0000	ASYNC
> 	0b1111	NI
> EndEnum

Thanks for the explanation. I made this a separate commit because I
considered people might object and HPMN0 is already an UnsignedEnum in
my previous commit.

Do you think it would be a good idea to make plain Enums signed by
default or should I just remove this commit from the series?


>> Signed-off-by: Colton Lewis <coltonlewis@...gle.com>
>> ---
>>    arch/arm64/tools/gen-sysreg.awk | 1 +
>>    1 file changed, 1 insertion(+)

>> diff --git a/arch/arm64/tools/gen-sysreg.awk  
>> b/arch/arm64/tools/gen-sysreg.awk
>> index f2a1732cb1f6..fa21a632d9b7 100755
>> --- a/arch/arm64/tools/gen-sysreg.awk
>> +++ b/arch/arm64/tools/gen-sysreg.awk
>> @@ -308,6 +308,7 @@ $1 == "Enum" && (block_current() == "Sysreg" ||  
>> block_current() == "SysregFields
>>    	parse_bitdef(reg, field, $2)

>>    	define_field(reg, field, msb, lsb)
>> +	define_field_sign(reg, field, "false")

>>    	next
>>    }

> Thanks,

> Ben

> [1]
> https://lore.kernel.org/all/20221207-arm64-sysreg-helpers-v4-1-25b6b3fb9d18@kernel.org/