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From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH 07/12] arm64: Treat HCR_EL2.E2H as RES1 when
 ID_AA64MMFR4_EL1.E2H0 is non-zero
Message-ID: <ZVeqcPAW7qGj0RJ8@thinky-boi>
References: <20231113174244.3026520-1-maz@kernel.org>
 <20231113174244.3026520-8-maz@kernel.org>
 <ZVaycYt51sUWS0h+@thinky-boi>
 <86wmugzi96.wl-maz@kernel.org>
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On Fri, Nov 17, 2023 at 12:17:25PM +0000, Marc Zyngier wrote:
> On Fri, 17 Nov 2023 00:23:13 +0000, Oliver Upton <oliver.upton@linux.dev> wrote:
> > Wouldn't it be more consistent with the architectural definition of
> > signed feature fields to just test the sign bit in this case?
> > 
> > Maybe like:
> > 
> > 	ubfx	x0, x0, #ID_AA64MMFR4_EL1_E2H0_SHIFT, #ID_AA64MMFR4_EL1_E2H0_WIDTH
> > 	tbnz	x0, #3, 1f
> > 
> > You'll also save 8 measly bytes of text while you're at it :)
> 
> At this stage, why not try this:
> 
> tbnz x0, #(ID_AA64MMFR4_EL1_E2H0_SHIFT + ID_AA64MMFR4_EL1_E2H0_WIDTH - 1), 1f
> 
> and we save a total of 12 bytes!

Ship it :)

-- 
Thanks,
Oliver