linux-kernel - Re: [PATCH v7 3/10] KVM: arm64: Move hyp_symbol

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Date:   Thu, 21 Mar 2019 10:59:08 +0530
From:   Amit Daniel Kachhap <amit.kachhap@....com>
To:     Julien Thierry <julien.thierry@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Christoffer Dall <christoffer.dall@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Jones <drjones@...hat.com>,
        Dave Martin <Dave.Martin@....com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
        kvmarm@...ts.cs.columbia.edu,
        Kristina Martsenko <kristina.martsenko@....com>,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>
Subject: Re: [PATCH v7 3/10] KVM: arm64: Move hyp_symbol_addr to fix
 dependency

Hi Julien,

On 3/20/19 2:19 PM, Julien Thierry wrote:
> Hi Amit,
> 
> On 19/03/2019 08:30, Amit Daniel Kachhap wrote:
>> Currently hyp_symbol_addr is palced in kvm_mmu.h which is mostly
>> used by __hyp_this_cpu_ptr in kvm_asm.h but it cannot include
>> kvm_mmu.h directly as kvm_mmu.h uses kvm_ksym_ref which is
>> defined inside kvm_asm.h. Hence, hyp_symbol_addr is moved inside
>> kvm_asm.h to fix this dependency on each other.
>>
>> Also kvm_ksym_ref is corresponding counterpart of hyp_symbol_addr
>> so should be ideally placed inside kvm_asm.h.
>>
> 
> This part is a bit confusing, it lead me to think that kvm_ksym_ref was
> in kvm_mmu.h and should moved to kvm_asm.h as well. I'd suggest
> rephrasing it with something along the lines:
> 
> "Also, hyp_symbol_addr corresponding counterpart, kvm_ksym_ref, is
> already in kvm_asm.h, making it more sensible to move kvm_symbol_addr to
> the same file."
ok, will rephrase.
> 
> Otherwise:
> 
> Reviewed-by: Julien Thierry <julien.thierry@....com>

Thanks,
Amit
> 
> Cheers,
> 
> Julien
> 
>> Suggested by: James Morse <james.morse@....com>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
>> Cc: Marc Zyngier <marc.zyngier@....com>
>> Cc: Christoffer Dall <christoffer.dall@....com>
>> Cc: kvmarm@...ts.cs.columbia.edu
>> ---
>>   arch/arm64/include/asm/kvm_asm.h | 20 ++++++++++++++++++++
>>   arch/arm64/include/asm/kvm_mmu.h | 20 --------------------
>>   2 files changed, 20 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
>> index f5b79e9..57a07e8 100644
>> --- a/arch/arm64/include/asm/kvm_asm.h
>> +++ b/arch/arm64/include/asm/kvm_asm.h
>> @@ -80,6 +80,26 @@ extern void __vgic_v3_init_lrs(void);
>>   
>>   extern u32 __kvm_get_mdcr_el2(void);
>>   
>> +/*
>> + * Obtain the PC-relative address of a kernel symbol
>> + * s: symbol
>> + *
>> + * The goal of this macro is to return a symbol's address based on a
>> + * PC-relative computation, as opposed to a loading the VA from a
>> + * constant pool or something similar. This works well for HYP, as an
>> + * absolute VA is guaranteed to be wrong. Only use this if trying to
>> + * obtain the address of a symbol (i.e. not something you obtained by
>> + * following a pointer).
>> + */
>> +#define hyp_symbol_addr(s)						\
>> +	({								\
>> +		typeof(s) *addr;					\
>> +		asm("adrp	%0, %1\n"				\
>> +		    "add	%0, %0, :lo12:%1\n"			\
>> +		    : "=r" (addr) : "S" (&s));				\
>> +		addr;							\
>> +	})
>> +
>>   /* Home-grown __this_cpu_{ptr,read} variants that always work at HYP */
>>   #define __hyp_this_cpu_ptr(sym)						\
>>   	({								\
>> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
>> index b0742a1..3dea6af 100644
>> --- a/arch/arm64/include/asm/kvm_mmu.h
>> +++ b/arch/arm64/include/asm/kvm_mmu.h
>> @@ -118,26 +118,6 @@ static inline unsigned long __kern_hyp_va(unsigned long v)
>>   #define kern_hyp_va(v) 	((typeof(v))(__kern_hyp_va((unsigned long)(v))))
>>   
>>   /*
>> - * Obtain the PC-relative address of a kernel symbol
>> - * s: symbol
>> - *
>> - * The goal of this macro is to return a symbol's address based on a
>> - * PC-relative computation, as opposed to a loading the VA from a
>> - * constant pool or something similar. This works well for HYP, as an
>> - * absolute VA is guaranteed to be wrong. Only use this if trying to
>> - * obtain the address of a symbol (i.e. not something you obtained by
>> - * following a pointer).
>> - */
>> -#define hyp_symbol_addr(s)						\
>> -	({								\
>> -		typeof(s) *addr;					\
>> -		asm("adrp	%0, %1\n"				\
>> -		    "add	%0, %0, :lo12:%1\n"			\
>> -		    : "=r" (addr) : "S" (&s));				\
>> -		addr;							\
>> -	})
>> -
>> -/*
>>    * We currently support using a VM-specified IPA size. For backward
>>    * compatibility, the default IPA size is fixed to 40bits.
>>    */
>>
>