linux-kernel - Re: [PATCH v1 17/24] kvm: arm64: Add __hyp_pa

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Date:   Mon, 9 Nov 2020 16:59:33 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        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>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Scull <ascull@...gle.com>,
        Andrew Walbran <qwandor@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v1 17/24] kvm: arm64: Add __hyp_pa_symbol helper macro

Hey David,

On Monday 09 Nov 2020 at 11:32:26 (+0000), David Brazdil wrote:
> Add helper macro for computing the PA of a kernel symbol in nVHE hyp
> code. This will be useful for computing the PA of a PSCI CPU_ON entry
> point.
> 
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/psci.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci.c b/arch/arm64/kvm/hyp/nvhe/psci.c
> index b0b5df590ba5..7510b9e174e9 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci.c
> @@ -20,6 +20,16 @@ s64 hyp_physvirt_offset;
>  
>  #define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset)
>  
> +#define __hyp_pa_symbol(sym)					\
> +	({							\
> +		extern char sym[];				\
> +		unsigned long kern_va;				\
> +								\
> +		asm volatile("ldr %0, =%1" : "=r" (kern_va)	\
> +					   : "S" (sym));	\
> +		kern_va - kimage_voffset;			\
> +	})
> +

Could this be simplified to __hyp_pa(hyp_symbol_addr(sym))? That would
avoid the dependency on kimage_voffset.

Thanks,
Quentin