linux-kernel - Re: [PATCH v2 2/6] arm64: trap to EL1 accesses to AMU counters from EL0

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Message-ID: <dcecb179-02f1-0608-6a84-5b2dd0bbcdb3@arm.com>
Date:   Thu, 23 Jan 2020 17:04:32 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Ionela Voinescu <ionela.voinescu@....com>, catalin.marinas@....com,
        will@...nel.org, mark.rutland@....com, maz@...nel.org,
        suzuki.poulose@....com, sudeep.holla@....com,
        dietmar.eggemann@....com
Cc:     peterz@...radead.org, mingo@...hat.com, ggherdovich@...e.cz,
        vincent.guittot@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Steve Capper <steve.capper@....com>
Subject: Re: [PATCH v2 2/6] arm64: trap to EL1 accesses to AMU counters from
 EL0

On 18/12/2019 18:26, Ionela Voinescu wrote:
> +/*
> + * reset_amuserenr_el0 - reset AMUSERENR_EL0 if AMUv1 present
> + */
> +	.macro	reset_amuserenr_el0, tmpreg
> +	mrs	\tmpreg, id_aa64pfr0_el1	// Check ID_AA64PFR0_EL1
> +	ubfx	\tmpreg, \tmpreg, #ID_AA64PFR0_AMU_SHIFT, #4
> +	cbz	\tmpreg, 9000f			// Skip if no AMU present
> +	msr_s	SYS_AMUSERENR_EL0, xzr		// Disable AMU access from EL0
> +9000:

AIUI you can steer away from the obscure numbering scheme and define the
label using the macro counter:

	cbz \tmpreg, .Lskip_\@
	[...]
.Lskip_\@:
	.endm


> +	.endm