linux-kernel - Re: [PATCH 2/2] KVM: arm64: Clarify meaning of _MASK and

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Message-ID: <87v80l48z3.wl-maz@kernel.org>
Date: Wed, 31 Jul 2024 21:12:00 +0100
From: Marc Zyngier <maz@...nel.org>
To: Mark Brown <broonie@...nel.org>
Cc: Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Fuad Tabba <tabba@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] KVM: arm64: Clarify meaning of _MASK and _nMASK for FGT registers

On Wed, 31 Jul 2024 19:58:38 +0100,
Mark Brown <broonie@...nel.org> wrote:
> 
> Since the use of _MASK to mean bits where setting the bit causes traps to
> be generated is a little unusual add a clarifying comment.
> 
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  arch/arm64/include/asm/kvm_arm.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index d347483395b4..1d8745740fb1 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -343,6 +343,10 @@
>   * FGT register definitions
>   *
>   * RES0 and polarity masks for the FGT registers.
> + *
> + * _RES0:  Bits which are RES0
> + * _MASK:  Bits which enable traps when set
> + * _nMASK: Bits which disable traps when set

The rest of the code call this "negative polarity". Also, in some
cases (such as with HCRX_EL2), such bits are *enable* bits. So you
probably want to capture this as well.

	M.

-- 
Without deviation from the norm, progress is not possible.