linux-kernel - Re: [PATCH] ARC: ARCv2: jump label: implement jump label patching

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Date:   Fri, 28 Jun 2019 22:59:33 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Alexey Brodkin" <Alexey.Brodkin@...opsys.com>,
        Jason Baron <jbaron@...hat.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Ard Biesheuvel" <ard.biesheuvel@...aro.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] ARC: ARCv2: jump label: implement jump label patching

On 6/18/19 9:16 AM, Vineet Gupta wrote:
> On 6/14/19 9:41 AM, Eugeniy Paltsev wrote:
>> Implement jump label patching for ARC. Jump labels provide
>> an interface to generate dynamic branches using
>> self-modifying code.
>>
>> This allows us to implement conditional branches where
>> changing branch direction is expensive but branch selection
>> is basically 'free'
>>
>> This implementation uses 32-bit NOP and BRANCH instructions
>> which forced to be aligned by 4 to guarantee that they don't
>> cross L1 cache line and can be update atomically.
>>
>> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> 
> LGTM overall - nits below.

@Peter can we have your reviewed/ack or some such assuming you don't have any
objections !

Thx,
-Vineet