linux-kernel - Re: [PATCH v1 01/13] arm64: mm: Re-implement the __tlbi

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Message-ID: <de91c62d-e7f8-4005-bb62-d3a2dfe57da4@arm.com>
Date: Fri, 2 Jan 2026 14:18:44 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
 Catalin Marinas <catalin.marinas@....com>,
 Mark Rutland <mark.rutland@....com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Oliver Upton <oliver.upton@...ux.dev>, Marc Zyngier <maz@...nel.org>,
 Dev Jain <dev.jain@....com>, Linu Cherian <Linu.Cherian@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 01/13] arm64: mm: Re-implement the __tlbi_level macro
 as a C function

Happy new year!


On 16/12/2025 17:53, Jonathan Cameron wrote:
> On Tue, 16 Dec 2025 14:45:46 +0000
> Ryan Roberts <ryan.roberts@....com> wrote:
> 
>> As part of efforts to reduce our reliance on complex preprocessor macros
>> for TLB invalidation routines, convert the __tlbi_level macro to a C
>> function for by-level TLB invalidation.
>>
>> Each specific tlbi level op is implemented as a C function and the
>> appropriate function pointer is passed to __tlbi_level(). Since
>> everything is declared inline and is statically resolvable, the compiler
>> will convert the indirect function call to a direct inline execution.
>>
>> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
>> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
>> ---
> 
>> +static __always_inline void __tlbi_level(tlbi_op op, u64 addr, u32 level)
>> +{
>> +	u64 arg = addr;
>> +
>> +	if (alternative_has_cap_unlikely(ARM64_HAS_ARMv8_4_TTL) && level <= 3) {
>> +		u64 ttl = level | (get_trans_granule() << 2);
>> +
>> +		arg &= ~TLBI_TTL_MASK;
>> +		arg |= FIELD_PREP(TLBI_TTL_MASK, ttl);
> 
> Probably don't care, but I think you could do
> 		FIELD_MODIFY(TLBI_TTL_MASK, &arg, ttl);
> instead of those two lines. Code generation hopefully similar?
> So depends on which macros you find more readable.

Yeah that's probably slightly neater - I'll switch to this for the next version.

Thanks,
Ryan

> 
>> +	}
>> +
>> +	op(arg);
>> +}
>>  
>>  #define __tlbi_user_level(op, arg, level) do {				\
>>  	if (arm64_kernel_unmapped_at_el0())				\
>