linux-kernel - Re: [PATCH v2 04/10] kvm: arm64: Remove hyp_adr/ldr_this

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Message-ID: <20200910123452.GD93664@google.com>
Date:   Thu, 10 Sep 2020 13:34:52 +0100
From:   Andrew Scull <ascull@...gle.com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Dennis Zhou <dennis@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Arnd Bergmann <arnd@...db.de>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, linux-arch@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v2 04/10] kvm: arm64: Remove hyp_adr/ldr_this_cpu

On Thu, Sep 03, 2020 at 11:17:06AM +0200, 'David Brazdil' via kernel-team wrote:
> The hyp_adr/ldr_this_cpu helpers were introduced for use in hyp code
> because they always needed to use TPIDR_EL2 for base, while
> adr/ldr_this_cpu from kernel proper would select between TPIDR_EL2 and
> _EL1 based on VHE/nVHE.
> 
> Simplify this now that the nVHE hyp mode case can be handled using the
> __KVM_NVHE_HYPERVISOR__ macro. VHE selects _EL2 with alternatives.
> 
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>

Acked-by: Andrew Scull <ascull@...gle.com>

> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 54d181177656..b392a977efb6 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -218,6 +218,21 @@ lr	.req	x30		// link register
>  	str	\src, [\tmp, :lo12:\sym]
>  	.endm
>  
> +	/*
> +	 * @dst: destination register (32 or 64 bit wide)
> +	 */
> +	.macro	this_cpu_offset, dst
> +#ifdef __KVM_NVHE_HYPERVISOR__
> +	mrs	\dst, tpidr_el2

Another part that might also apply to __KVM_VHE_HYPERVISOR__.

> +#else
> +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
> +	mrs	\dst, tpidr_el1
> +alternative_else
> +	mrs	\dst, tpidr_el2
> +alternative_endif
> +#endif
> +	.endm