Re: [PATCH 2/2] selftests: KVM: Fix 'asm-operand-width' warnings in steal_time.c

[Andrew Jones <drjones@xxxxxxxxxx>]

On Tue, Sep 21, 2021 at 01:01:20AM +0000, Oliver Upton wrote:
> Building steal_time.c for arm64 with clang throws the following:
> 
> >> steal_time.c:130:22: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
>           : "=r" (ret) : "r" (func), "r" (arg) :
>                               ^
> >> steal_time.c:130:34: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
>           : "=r" (ret) : "r" (func), "r" (arg) :
>                                           ^
> 
> Silence by casting operands to 64 bits.
> 
> Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/steal_time.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
> index ecec30865a74..eb75b31122c5 100644
> --- a/tools/testing/selftests/kvm/steal_time.c
> +++ b/tools/testing/selftests/kvm/steal_time.c
> @@ -127,7 +127,7 @@ static int64_t smccc(uint32_t func, uint32_t arg)
>  		"mov	x1, %2\n"
>  		"hvc	#0\n"
>  		"mov	%0, x0\n"
> -	: "=r" (ret) : "r" (func), "r" (arg) :
> +	: "=r" (ret) : "r" ((uint64_t)func), "r" ((uint64_t)arg) :

Actually, I think I'd rather fix this smccc implementation to match the
spec, which I think should be done like this

diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index ecec30865a74..7da957259ce4 100644
--- a/tools/testing/selftests/kvm/steal_time.c
+++ b/tools/testing/selftests/kvm/steal_time.c
@@ -118,12 +118,12 @@ struct st_time {
        uint64_t st_time;
 };
 
-static int64_t smccc(uint32_t func, uint32_t arg)
+static int64_t smccc(uint32_t func, uint64_t arg)
 {
        unsigned long ret;
 
        asm volatile(
-               "mov    x0, %1\n"
+               "mov    w0, %w1\n"
                "mov    x1, %2\n"
                "hvc    #0\n"
                "mov    %0, x0\n"


Thanks,
drew

>  	  "x0", "x1", "x2", "x3");
>  
>  	return ret;
> -- 
> 2.33.0.464.g1972c5931b-goog
>