Re: [PATCH v3 01/22] arm64: Add macros to read/write system registers

[Catalin Marinas]

On Mon, Dec 07, 2015 at 10:53:17AM +, Marc Zyngier wrote:
> From: Mark Rutland 
> 
> Rather than crafting custom macros for reading/writing each system
> register provide generics accessors, read_sysreg and write_sysreg, for
> this purpose.
> 
> Unlike read_cpuid, calls to read_exception_reg are never expected
> to be optimized away or replaced with synthetic values.

What's read_exception_reg? Is it a macro somewhere?

> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index d48ab5b..c9c283a 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -20,6 +20,8 @@
>  #ifndef __ASM_SYSREG_H
>  #define __ASM_SYSREG_H
>  
> +#include 
> +
>  #include 
>  
>  /*
> @@ -208,6 +210,8 @@
>  
>  #else
>  
> +#include 
> +
>  asm(
>  ".irp
> num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n"
>  ".equ__reg_num_x\\num, \\num\n"
> @@ -232,6 +236,19 @@ static inline void config_sctlr_el1(u32 clear, u32 set)
>   val |= set;
>   asm volatile("msr sctlr_el1, %0" : : "r" (val));
>  }
> +
> +#define read_sysreg(r) ({\
> + u64 __val;  \
> + asm volatile("mrs %0, " __stringify(r) : "=r" (__val)); \
> + __val;  \
> +})

And maybe a comment here on why this is always volatile.

Otherwise:

Acked-by: Catalin Marinas 

-- 
Catalin
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Re: [PATCH v3 01/22] arm64: Add macros to read/write system registers

[Mark Rutland]

On Mon, Dec 07, 2015 at 05:35:20PM +, Catalin Marinas wrote:
> On Mon, Dec 07, 2015 at 10:53:17AM +, Marc Zyngier wrote:
> > From: Mark Rutland 
> > 
> > Rather than crafting custom macros for reading/writing each system
> > register provide generics accessors, read_sysreg and write_sysreg, for
> > this purpose.
> > 
> > Unlike read_cpuid, calls to read_exception_reg are never expected
> > to be optimized away or replaced with synthetic values.
> 
> What's read_exception_reg? Is it a macro somewhere?

That was what read_sysreg used to be called on a local branch of mine. I
didn't spot that when reworking the patch.

So s/read_exception_reg/read_sysreg/ here.

> > +#define read_sysreg(r) ({  \
> > +   u64 __val;  \
> > +   asm volatile("mrs %0, " __stringify(r) : "=r" (__val)); \
> > +   __val;  \
> > +})
> 
> And maybe a comment here on why this is always volatile.

Makes sense to me.

Marc, are you happy to turn the last sentence from the commit message
into a comment here (with the substitution)?

Thanks,
Mark.
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Re: [PATCH v3 01/22] arm64: Add macros to read/write system registers

[Marc Zyngier]

On 07/12/15 17:45, Mark Rutland wrote:
> On Mon, Dec 07, 2015 at 05:35:20PM +, Catalin Marinas wrote:
>> On Mon, Dec 07, 2015 at 10:53:17AM +, Marc Zyngier wrote:
>>> From: Mark Rutland 
>>>
>>> Rather than crafting custom macros for reading/writing each system
>>> register provide generics accessors, read_sysreg and write_sysreg, for
>>> this purpose.
>>>
>>> Unlike read_cpuid, calls to read_exception_reg are never expected
>>> to be optimized away or replaced with synthetic values.
>>
>> What's read_exception_reg? Is it a macro somewhere?
> 
> That was what read_sysreg used to be called on a local branch of mine. I
> didn't spot that when reworking the patch.
> 
> So s/read_exception_reg/read_sysreg/ here.
> 
>>> +#define read_sysreg(r) ({  \
>>> +   u64 __val;  \
>>> +   asm volatile("mrs %0, " __stringify(r) : "=r" (__val)); \
>>> +   __val;  \
>>> +})
>>
>> And maybe a comment here on why this is always volatile.
> 
> Makes sense to me.
> 
> Marc, are you happy to turn the last sentence from the commit message
> into a comment here (with the substitution)?

Sure, I'll update the patch and push the branch out again, together with
Catalin's Ack.

Thanks,

M.
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