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

[mark.rutland@arm.com (Mark Rutland)]

On Mon, Dec 07, 2015 at 05:35:20PM +0000, Catalin Marinas wrote:
> On Mon, Dec 07, 2015 at 10:53:17AM +0000, Marc Zyngier wrote:
> > From: Mark Rutland <mark.rutland@arm.com>
> > 
> > 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.