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

Paolo Bonzini
2021-09-21T17:38:23Z

On 21/09/21 09:19, Andrew Jones wrote:
> 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@google.com>
>> ---
>> 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"
>

Agreed, can you send out a patch? Thanks,

Paolo