[PATCH 3/8] arm64: Add new hcall HVC_CALL_FUNC

[geoff@infradead.org (Geoff Levand)]

Hi Catalin,


On Tue, 2015-01-27 at 17:39 +0000, Catalin Marinas wrote:
> On Sat, Jan 17, 2015 at 12:23:34AM +0000, Geoff Levand wrote:
> > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
> > index 99c319c..4f23a48 100644
> > --- a/arch/arm64/include/asm/virt.h
> > +++ b/arch/arm64/include/asm/virt.h
> > @@ -41,6 +41,19 @@
> >  
> >  #define HVC_CALL_HYP 3
> >  
> > +/*
> > + * HVC_CALL_FUNC - Execute a function at EL2.
> > + *
> > + * @x0: Physical address of the function to be executed.
> > + * @x1: Passed as the first argument to the function.
> > + * @x2: Passed as the second argument to the function.
> > + * @x3: Passed as the third argument to the function.
> > + *
> > + * The called function must preserve the contents of register x18.
> 
> Can you pick a register that's normally callee saved?

Mark covered this in his reply.

> > + */
> > +
> > +#define HVC_CALL_FUNC 4
> > +
> >  #ifndef __ASSEMBLY__
> >  
> >  /*
> > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
> > index e3db3fd..b5d36e7 100644
> > --- a/arch/arm64/kernel/hyp-stub.S
> > +++ b/arch/arm64/kernel/hyp-stub.S
> > @@ -66,9 +66,20 @@ el1_sync:
> >  	mrs	x0, vbar_el2
> >  	b	2f
> >  
> > -1:	cmp	x18, #HVC_SET_VECTORS
> > -	b.ne	2f
> > -	msr	vbar_el2, x0
> > +1:	cmp     x18, #HVC_SET_VECTORS
> 
> This line doesn't seem to have any change, apart from some whitespace.
> Or did you want to drop the label?

Some whitespace problems got in there from so many rebases.  I went
through the series and cleaned them up.


> > +	b.ne    1f
> > +	msr     vbar_el2, x0
> > +	b       2f
> > +
> > +1:	cmp     x18, #HVC_CALL_FUNC
> > +	b.ne    2f
> > +	mov     x18, lr
> > +	mov     lr, x0
> > +	mov     x0, x1
> > +	mov     x1, x2
> > +	mov     x2, x3
> > +	blr     lr
> > +	mov     lr, x18
> >  
> >  2:	eret
> >  ENDPROC(el1_sync)
> 
> What is the calling convention for this HVC? You mentioned x18 above but
> what about other registers that the called function may corrupt (x18 is
> a temporary register, so it's not expected to be callee saved).

Again, Mark covered this in his reply.