linux-kernel - Re: [PATCH 11/14] arm64: KVM: Add HYP per-cpu accessors

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Date:   Thu, 24 May 2018 13:11:35 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christoffer Dall <christoffer.dall@....com>
Subject: Re: [PATCH 11/14] arm64: KVM: Add HYP per-cpu accessors

On Tue, May 22, 2018 at 04:06:45PM +0100, Marc Zyngier wrote:
> As we're going to require to access per-cpu variables at EL2,
> let's craft the minimum set of accessors required to implement
> reading a per-cpu variable, relying on tpidr_el2 to contain the
> per-cpu offset.
> 
> Reviewed-by: Christoffer Dall <christoffer.dall@....com>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>

Reviewed-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/include/asm/kvm_asm.h | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index f6648a3e4152..fefd8cf42c35 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -71,14 +71,37 @@ extern u32 __kvm_get_mdcr_el2(void);
>  
>  extern u32 __init_stage2_translation(void);
>  
> +/* Home-grown __this_cpu_{ptr,read} variants that always work at HYP */
> +#define __hyp_this_cpu_ptr(sym)						\
> +	({								\
> +		void *__ptr = hyp_symbol_addr(sym);			\
> +		__ptr += read_sysreg(tpidr_el2);			\
> +		(typeof(&sym))__ptr;					\
> +	 })
> +
> +#define __hyp_this_cpu_read(sym)					\
> +	({								\
> +		*__hyp_this_cpu_ptr(sym);				\
> +	 })
> +
>  #else /* __ASSEMBLY__ */
>  
> -.macro get_host_ctxt reg, tmp
> -	adr_l	\reg, kvm_host_cpu_state
> +.macro hyp_adr_this_cpu reg, sym, tmp
> +	adr_l	\reg, \sym
>  	mrs	\tmp, tpidr_el2
>  	add	\reg, \reg, \tmp
>  .endm
>  
> +.macro hyp_ldr_this_cpu reg, sym, tmp
> +	adr_l	\reg, \sym
> +	mrs	\tmp, tpidr_el2
> +	ldr	\reg,  [\reg, \tmp]
> +.endm
> +
> +.macro get_host_ctxt reg, tmp
> +	hyp_adr_this_cpu \reg, kvm_host_cpu_state, \tmp
> +.endm
> +
>  .macro get_vcpu_ptr vcpu, ctxt
>  	get_host_ctxt \ctxt, \vcpu
>  	ldr	\vcpu, [\ctxt, #HOST_CONTEXT_VCPU]
> -- 
> 2.14.2
>