Re: [PATCH v5 1/3] util: Add functions for s390x mmio read/write

[Farhan Ali <alifm@linux.ibm.com>]

On 4/25/2025 7:09 AM, Heiko Carstens wrote:
> On Fri, Apr 25, 2025 at 12:29:35PM +0200, Niklas Schnelle wrote:
>> On Fri, 2025-04-25 at 11:00 +0200, Thomas Huth wrote:
>>> On 17/04/2025 19.37, Farhan Ali wrote:
>>>> +    asm volatile(
>>>> +        /* pcilgi */
>>>> +        ".insn   rre,0xb9d60000,%[val],%[ioaddr_len]\n"
>>>> +        "ipm     %[cc]\n"
>>>> +        "srl     %[cc],28\n"
>>>> +        : [cc] "=d"(cc), [val] "=d"(val),
>>>> +        [ioaddr_len] "+&d"(ioaddr_len.pair) :: "cc");
>>> Do we need the "&" modifier here? ... at least the kernel does not seem to
>>> use it ...
>>  From my understanding it's not strictly needed, but I also used it in
>> the rdma-core user-space code where I had pointed Farhan. I looked at
> It is not needed, since all inputs are consumed before to any output
> is written to.

Ack, will update the patch.


>>>> +    asm volatile (
>>>> +        /* pcistgi */
>>>> +        ".insn   rre,0xb9d40000,%[val],%[ioaddr_len]\n"
>>>> +        : [ioaddr_len] "+&d" (ioaddr_len.pair)
>>> dito
> Same here, it is not needed.

Ack, will update the patch here as well.

Thanks
Farhan