[kvm-unit-tests PATCH] powerpc/spapr_hcall: Fix assembler constraints of the h_random h-call

[kvm-unit-tests PATCH] powerpc/spapr_hcall: Fix assembler constraints of the h_random h-call

[Thomas Huth]

As noted by Laurent Vivier, a register that is marked with "+r" as
input and output is not required to be listed in the set of input
registers anymore.
And as noted by David Gibson, the sPAPR hypercall is also allowed to
clobber a bunch of other registers. According to the LoPAPR spec,
r0 and r3-r12, CTR, XER and CC registers are volatile, so we should
mark them in the clobber list.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 powerpc/spapr_hcall.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/powerpc/spapr_hcall.c b/powerpc/spapr_hcall.c
index 46731e1..dbff630 100644
--- a/powerpc/spapr_hcall.c
+++ b/powerpc/spapr_hcall.c
@@ -96,7 +96,9 @@ static int h_random(uint64_t *val)
 	register uint64_t r3 asm("r3") = H_RANDOM;
 	register uint64_t r4 asm("r4");
 
-	asm volatile (" sc 1 " : "+r"(r3), "=r"(r4) : "r"(r3));
+	asm volatile (" sc 1 "	: "+r"(r3), "=r"(r4) :
+				: "r0", "r5", "r6", "r7", "r8", "r9", "r10",
+				  "r11", "r12", "xer", "ctr", "cc");
 	*val = r4;
 
 	return r3;
-- 
1.8.3.1

Re: [kvm-unit-tests PATCH] powerpc/spapr_hcall: Fix assembler constraints of the h_random h-call

[Paolo Bonzini]

On 03/03/2016 12:23, Thomas Huth wrote:
> As noted by Laurent Vivier, a register that is marked with "+r" as
> input and output is not required to be listed in the set of input
> registers anymore.
> And as noted by David Gibson, the sPAPR hypercall is also allowed to
> clobber a bunch of other registers. According to the LoPAPR spec,
> r0 and r3-r12, CTR, XER and CC registers are volatile, so we should
> mark them in the clobber list.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  powerpc/spapr_hcall.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/powerpc/spapr_hcall.c b/powerpc/spapr_hcall.c
> index 46731e1..dbff630 100644
> --- a/powerpc/spapr_hcall.c
> +++ b/powerpc/spapr_hcall.c
> @@ -96,7 +96,9 @@ static int h_random(uint64_t *val)
>  	register uint64_t r3 asm("r3") = H_RANDOM;
>  	register uint64_t r4 asm("r4");
>  
> -	asm volatile (" sc 1 " : "+r"(r3), "=r"(r4) : "r"(r3));
> +	asm volatile (" sc 1 "	: "+r"(r3), "=r"(r4) :
> +				: "r0", "r5", "r6", "r7", "r8", "r9", "r10",
> +				  "r11", "r12", "xer", "ctr", "cc");
>  	*val = r4;
>  
>  	return r3;
> 

Applied, thanks.

Paolo