linux-kernel - Re: [PATCH v2 07/11] arm64: mops: handle MOPS exceptions

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Message-ID: <ZH3Pa/Ct3XX613Yj@arm.com>
Date:   Mon, 5 Jun 2023 13:04:59 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Shaoqin Huang <shahuang@...hat.com>
Cc:     Kristina Martsenko <kristina.martsenko@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Luis Machado <luis.machado@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/11] arm64: mops: handle MOPS exceptions

On Mon, Jun 05, 2023 at 07:43:27PM +0800, Shaoqin Huang wrote:
> Hi Kristina,
> 
> On 5/9/23 22:22, Kristina Martsenko wrote:
> > The memory copy/set instructions added as part of FEAT_MOPS can take an
> > exception (e.g. page fault) part-way through their execution and resume
> > execution afterwards.
> > 
> > If however the task is re-scheduled and execution resumes on a different
> > CPU, then the CPU may take a new type of exception to indicate this.
> > This is because the architecture allows two options (Option A and Option
> > B) to implement the instructions and a heterogeneous system can have
> > different implementations between CPUs.
> > 
> > In this case the OS has to reset the registers and restart execution
> > from the prologue instruction. The algorithm for doing this is provided
> > as part of the Arm ARM.
> 
> What is the Arm ARM? I'm not quite understand it.

The Arm Architecture Reference Manual:

https://developer.arm.com/documentation/ddi0487/latest

(the acronym we pretty well known among the arm/arm64 developers)

-- 
Catalin